Common Asthma Triggers

Read on to learn about common asthma triggers.

In 1981, the number of adults admitted to hospitals in Barcelona suffering from asthma rose dramatically, but only at certain times. After two years trying to track down the cause, doctors realized that soybean dust released into the atmosphere during loading and unloading at the city’s docks triggered the outbreaks. As this shows, environmental factors can trigger asthma in sensitive people, but identifying the cause can prove difficult. You may need to examine possible triggers at home, at work and at play.

Some asthma triggers (such as infections and exercise) overlap with the types of asthma we considered in the previous article. In this article, we will look at some other common asthma triggers

Jack’s new hobby

Jack, a 35-year-old local government accountant, rarely leaves his office during work hours. But Jack plays rugby and cricket for his local village sides and is relatively fit. He’s never suffered from breathing or chest problems before, but recently started feeling breathless at home and is waking several nights a week, coughing. Jack sees his GP as he’s concerned about heart disease. However, his doctor realizes that Jack’s developed asthma and tries to track down any obvious causes before referring for allergy testing. Jack bought his daughter a rabbit for her eighth birthday around the time the symptoms started, but his work commitments mean that he rarely comes into contact with the pet. The only other change has been that Jack’s restarted an old hobby: electronics. He’s currently building a new computer. The symptoms, Jack now recalls, started a month or so after he started working on the computer. The GP suggests that the solder – a common trigger for occupational asthma – may be responsible. After taking a break from his hobby for a couple of weeks, Jack’s symptoms improve.

Allergens as asthma triggers

The immune system evolved to recognize and eradicate invading micro-organisms. In people with allergic asthma, an allergen (immune trigger) inappropriately triggers the immune defences. However, while the immune system clears an invading bacterium, allergic asthma arises from chronic inflammation. For example, in children and young adults, being sensitive on skin-prick tests to indoor allergens (such as house dust mite or cat and dog dander) and the fungus Alternaria increases the risk of developing asthma between three- and twenty-fold. Furthermore, Ségala and colleagues found that adults who had asthma in childhood were more likely than those who developed asthma as adults to be sensitive to allergens such as house dust mite, dog hair, and grass and tree pollens.


Fewer than 100 of the more than a quarter of a million plant species worldwide that produce pollen trigger asthma or other allergies in humans. Unfortunately, the 100 includes some of the most common plants and pollen is a common asthma trigger. In the UK, for example, grass, tree and nettle are the most common pollen allergens. However, a wide variety of other flora can trigger asthma and other allergies, including some relatively exotic ornamental plants, such as Ficus benjamina (weeping fig or Benjamin’s fig) and mimosa. Not surprisingly, the allergen responsible for pollen-related asthma varies worldwide as the flora changes. For example, between 10 and 20 per cent of Americans suffer from ragweed allergy, which can cause hay fever and asthma. Indeed, three-quarters of Americans who are allergic to pollen are sensitive to ragweed.

You don’t need to live next to a meadow or wood to suffer pollen-triggered asthma. Some pollens travel 20 km from their source. Scientists found ragweed pollen 400 miles out to sea and two miles high in the atmosphere. On the other hand, grass pollen deposits within three metres of the parent plant. But grass is everywhere, even in the centre of towns and cities. Just think how quickly grass colonizes an urban wasteland. This makes avoiding grass pollen difficult, if not impossible. Nevertheless, you can take several steps to reduce your exposure.


Fungi are remarkably diverse. Biologists have identified more than 70,000 fungal species. Thousands more probably await discovery. Indeed, some mycologists estimate that 1.5 million species of fungi may exist amid life on earth, each of which has its own niche. The moulds around damp windows, yeasts used in bread and beer-making, and dermatophytes that colonize skin, hair and nails are all fungi.

Many fungi potentially pose health problems. AIDS patients, for example, can die from opportunistic fungal infections. The yeast Candida albicans causes vaginal and oral thrush – the latter can be a problem with inhaled steroids – while dermatophytes cause athlete’s foot, ringworm and ‘jock itch’. And several fungi can trigger asthma.

For example, the fungi Cladosporium and Alternaria grow on dead organic material (such as decaying leaves). Levels of spores from these fungi peak around harvest time and can trigger severe asthma attacks in some people working outside. Furthermore, around 400 species of mould make their homes indoors. Look at the corner of a window where water collects or in the bathroom of a poorly ventilated house. The dark stain could be a mould such as Aspergillus or Penicillium, both of which can trigger asthma in sensitized people.

Indeed, moulds can grow almost anywhere, provided there’s enough moisture and oxygen – even inside our lungs. Fairs and colleagues grew Aspergillus fumigatus from the sputum of 63 per cent of asthma patients who produced IgE specific for the fungus, 31 per cent of non-sensitized asthmatics and 7 per cent of healthy people. However, unlike plants, moulds can’t produce food from sunlight and air, so they decompose plant or animal matter for nourishment. While moulds don’t – unlike plants – have a reproductive season, warmth and high humidity tends to encourage their growth. As a result, spore levels peak in warm humid weather and are particularly high in bathrooms, showers and kitchens.

House dust mites are a  very common asthma trigger

It’s an unpleasant thought, but your beds, soft toys and carpets are home to millions of microscopic creatures that feed on dead skin cells and other debris – the ubiquitous house dust mite. A gram of house dust may contain up to 5,000 mites.

House dust mites are most at home in bedding, soft furnishings and dusty corners where there is plenty of dead skin. So you probably spend eight hours each night lying among the two million mites in a typical bed mattress. Meanwhile, the mites use enzymes to digest your dead skin cells. The enzymes accumulate in the mites’ faeces. When inhaled, the enzymes can trigger the reaction that leads to asthma.


The UK is home to some 10.3 million cats and 10.5 million dogs. In 2007, 26 per cent of households owned cats and 31 per cent owned dogs, according to the Veterinary Record. We also own numerous other pets including fish, birds, horses, reptiles and other more exotic species. Furthermore, many people work with animals, in food production, science laboratories, zoos and pet shops. Not surprisingly, asthma and allergies triggered by animals are common.

Animals can shed particles of dead skin and hair (dander) or feathers that can cause severe allergies in sensitive people. So people who keep pigeons, budgerigars or other birds can become sensitive to feathers and develop ‘pigeon fancier’s lung’. Some people also become allergic to a particular animal’s urine.

If you’re allergic to an exotic, laboratory or farm animal, it’s probably easy to limit your exposure and to avoid these particular asthma triggers. Avoiding allergens from domestic animals is more difficult, especially as few families want to rehome their loved pets. In any case, cat dander can cling to floors, soft furnishings and even the walls, so allergen levels can remain high more than nine months after the animal’s removal. Furthermore, cats and dogs spread dander as they roam the house. Allergies caused by cats and dogs tend to worsen during the winter, when the house is less well ventilated and pets spend more time indoors. However, you can reduce your exposure. 

Food allergies

Many parents believe that food allergies cause or contribute to their child’s asthma and act as asthma triggers. However, ‘true’ food allergies (in other words, caused by IgE specific for a protein in food) are very rare. For example, around 13 per cent of adults complain that certain foods trigger symptoms, such as asthma or intestinal complaints. However, only between one in every 500 and 10,000 adults are truly allergic.

Nevertheless, even if IgE isn’t responsible for your symptoms, you may be intolerant to preservatives or colours, for example. (We’ve already seen that some preservatives are chemically related to salicylates and may trigger symptoms in people with aspirin-sensitive asthma.) If you feel that food causes or exacerbates your symptoms, you should keep a diary and discuss undergoing a specific test for antibodies to suspected foods with your GP or asthma nurse. If this suggests that a food may contribute to your asthma, a dietician will help you exclude it from your diet to see if your symptoms improve. You may also undergo a ‘provocation’ test to see if reintroducing the food triggers symptoms.

But don’t be tempted to exclude the food from your diet yourself (you could cut out some important nutrients). And don’t be tempted by ‘alternative’ diagnostic tests for food sensitivity. Little, if any, scientific evidence supports their use.


Physicians, scientists, and laypeople have long believed that stress contributes to exacerbations of asthma. However, it has only been in the past two decades that convincing scientific evidence has accumulated to substantiate this hypothesis. For example, in an 18-month prospective study of children with asthma, the experience of an acute negative life event (e.g., death of a close family member) increased the risk of a subsequent asthma attack by nearly 2-fold (Sandberg et al., 2000). The impact of an acute negative event was accentuated when it occurred in the context of chronic stress. Children exposed to high levels of acute and chronic stress showed a 3-fold increase in risk for an attack in the two weeks that followed the acute event. Despite the recent empirical evidence linking stress with the clinical profile of asthma, much remains to be learned about the biological mechanisms underlying this phenomenon. 


In some people, emotional excitement or physical exertion during sex can trigger an asthma attack, so the tips on managing exercise-induced asthma may help. Using a bronchodilator before sex may help prevent you becoming breathless for the wrong reasons.

Occasionally, highly sensitive people with asthma suffer an attack if they kiss someone who has consumed a food or medicine (such as NSAIDs) that triggers their asthma exacerbations. Allergic people can be exquisitely sensitive, sometimes reacting several hours after their partner ingested the food or drug and even after they’ve brushed their teeth. Indeed, people may excrete certain triggers in their saliva as long as 16 to 24 hours after their body has absorbed the food or medicine. Furthermore, a few people are allergic to chemicals in spermicides, lubricants, latex (used in some condoms) or semen. Once again, keeping a diary and informing your partner of any drugs or foods that exacerbate your asthma may help reduce the risk of exacerbations and enable you to decide on what are your asthma triggers. 

Diseases linked to asthma

Asthma is one of the most common diseases in the UK. So, not surprisingly, many people suffer from one or more ailments in addition to asthma. Many of these ‘concurrent’ diseases have no impact on asthma or its treatment. But in some cases the concurrent disease undermines asthma control:

  • Some diseases – such as arthritis – may make using inhalers difficult. Changing the inhaler, using an aid or, in some cases, oral medications can overcome problems caused by poor mobility.
  • As we’ve seen with NSAIDs and beta-blockers, some medicines used to treat the concurrent disease can exacerbate asthma. Fortunately, doctors can usually find an alternative.
  • Some diseases directly increase the risk of developing asthma or suffering an exacerbation. The rest of this article looks at some common examples.

Hay fever

We tend to regard rhinitis – inflammation of the nose, such as in hay fever – and asthma as separate diseases. However, the respiratory tract is a continuous organ that begins in the nose and ends at the alveoli. In addition, in many people with both diseases, the same trigger (e.g. pollen) underlies allergic rhinitis and asthma. (We’ll see a striking example of this when we look at the effect of weather on asthma.) Indeed, inflammation that begins in the nose can spread to the lungs (or vice versa), eventually spreading throughout the entire respiratory tract. So people with asthma often develop rhinitis and vice versa. For example, occupational rhinitis is up to three times more common than work-related asthma. However, Rachiotis and co-workers reported that between 76 and 92 per cent of people with occupational asthma also suffer from rhinitis.

On the other hand, this intimate relationship means that treating rhinitis can improve asthma – and vice versa. For example, steroid nasal sprays that alleviate rhinitis can reduce bronchial hyper-responsiveness. So if you also suffer from hay fever or perennial rhinitis (non-seasonal symptoms caused by, for example, animal allergens or house dust mites) you should ask your nurse or GP to help you optimize treatment of your nasal symptoms.

Chronic sinusitis and polyps

Sinuses are small cavities behind your cheekbones, eyes and forehead, and on either side of the bridge of your nose. These cavities open into your nasal airways and help control the temperature and water content of the air that enters your lungs. (As we’ve seen, cold, dry air can trigger asthma symptoms.)

Sinusitis occurs when the sinuses become inflamed and swollen, often during a common cold, influenza or another infection. Exposure to allergens or irritants – including air pollution, tobacco smoke and chemicals such as pesticides, disinfectants and household detergents – can also trigger or exacerbate sinusitis.

Usually, mucus produced by your sinuses drains into your nose through small channels. Infections and inflammation can block these channels and mucus fills the sinus, causing pain, tender areas on the face, a blocked or runny nose, and, in some cases, a fever. On average, sinusitis takes about two and a half weeks to resolve. Chronic sinusitis, which lasts more than 12 weeks, increases an adult’s risk of developing asthma.

In some cases, for reasons that doctors don’t fully understand, tissues lining the sinuses can swell and expand into the nose, forming a polyp (see pictures below). Some polyps seem to grow after an infection. In others, allergies may be responsible. In both cases, polyps hinder nasal breathing, impair smell and may increase the risk of asthma. For example, around a third of people with intrinsic asthma suffer from sinusitis and nasal polyps. And 39 per cent of people with aspirin-induced asthma have intrinsic asthma and nasal polyps. So you may want to discuss your options for treating chronic sinusitis and nasal polyps with your doctor.

common asthma triggers- picture of sinus cavities in head

Above: The location of the sinuses in the head

asthma triggers - picture of sinus with polyps

Above: Nasal polyps in sinuses

common asthma triggers - picture of sinus showing nasal polyps

Above: The sinuses and polyps – side view


Most of us regard a bout of heartburn as the inevitable price for overindulging in spicy or fatty food, alcohol or caffeine, or as yet another consequence of smoking. Indeed, around a third of UK adults have endured the discomfort of heartburn at least once in the last six months. Around a quarter of adults experience heartburn at least monthly and 5 per cent suffer heartburn daily. Furthermore, between 10 and 20 per cent of adults experience GORD, one common cause of heartburn, on at least one day a week. However, people over 65 years of age seem to be especially likely to develop GORD. But don’t underestimate this common problem.

Don’t dismiss dyspepsia

Dyspepsia can arise from several causes, from overindulgence to potentially fatal cancers. So, if you start experiencing unexplained and persistent heartburn it’s worth seeking your GP’s advice, especially if you’re aged 55 years or older, or experience other symptoms, such as unintentional weight loss, difficulty swallowing, vomiting or signs of anaemia. And GORD occasionally causes potentially serious complications, including:

  • strictures (abnormal narrowing) in the food pipe (oesophagus) that cause swallowing difficulties;
  • ulcers in the oesophagus (food pipe);
  • a condition called Barrett’s oesophagus, where damage to the food pipe results in potentially cancerous cells replacing healthy cells in the lower oesophagus.

Barrett’s oesophagus is an influential risk factor for a type of cancer called oesophageal adenocarcinoma (OAC). According to Cancer Research UK, between 0.5 and 2 per cent of adults in Western countries probably have Barrett’s oesophagus. About 0.5 to 1 per cent of these develop OAC each year. While the absolute risk may be low, patients with Barrett’s oesophagus remain 30 to 125 times more likely to develop OAC than the general population.

GORD (or GERD- US) occurs when the stomach’s contents enter the oesophagus. Normally, a valve (sphincter) at the junction of the stomach and oesophagus prevents this ‘reflux’. However, certain meals, changes in posture (especially lying down), certain medications (including some drugs used to treat asthma – see page 43) and stress may weaken the sphincter, allowing reflux. As almost everyone suffers indigestion occasionally, gastroenterologists usually diagnose GORD only if patients suffer heartburn on at least one day each week.

Heartburn, GORD’s main manifestation, arises as the stomach’s contents burn the oesophagus. However, other symptoms include:

  • regurgitation of food or acid;
  • waterbrash – regurgitation of watery sour or tasteless acid;
  • a sudden gush of saliva;
  • chest pain;
  • cough;
  • hoarseness or sore throat;
  • bloating, belching, nausea.

See: Acid Reflux Disease for detailed information

Apart from causing some symptoms reminiscent of asthma (such as cough), people with GORD may regurgitate small amounts of stomach acid into their mouths, from where it can seep into their tracheas and lungs. Reflux is especially likely when you lie flat – gravity no longer helps prevent regurgitation. So GORD patients with asthma are especially likely to experience night-time wheezing, breathlessness and cough, and to produce phlegm in the morning. Indeed, Calhoun noted that 9 per cent of GORD patients had asthma, more than twice the number in subjects without GORD (4 per cent). GORD may also exacerbate the variation in lung function and the airway obstruction in people with asthma.

Certain people find that treating GORD relieves some symptoms of their asthma (particularly a bothersome cough). A review of trials by Gibson and colleagues that examined the link between asthma and GORD reported that omeprazole (a drug that reduces acid production by the stomach) improved FEV1 (a measure of lung function – see Chapter 5) by 20 per cent in four of 14 people with asthma. Overall, the average improvement was 10 per cent. Studies using other anti-reflux drugs failed to find any improvement in lung function. However, asthma symptoms – such as limitation of activity, shortness of breath and wheezing – can improve without objective improvements in lung function. So it’s certainly worth treating dyspepsia.

You can buy omeprazole and some other GORD treatments over the counter from pharmacists. Doctors can prescribe higher doses of these drugs and offer a wider choice of treatments for GORD. So, if you feel that GORD is making your symptoms worse, talk to your pharmacist or doctor. (But always let them know you have asthma.) You can also make some lifestyle changes that may alleviate GORD:

  • Obesity, smoking, alcohol, coffee and chocolate may transiently relax the sphincter. Fatty foods may slow the rate at which the stomach empties. Both of these changes can contribute to GORD. That’s yet another good reason to lose weight, quit smoking and eat a healthy diet.
  • As lying flat often makes matters worse, some people find that raising the head of the bed alleviates GORD. (You could try propping the head of your bed up on bricks.)
  • You should also avoid eating close to your bedtime. Food stimulates your stomach to produce acid.

Asthma drugs and GORD

Certain treatments for asthma can exacerbate GORD. For example, beta-agonists, anticholinergics and theophylline alleviate asthma symptoms by relaxing the ring of muscle surrounding the airways. But the same mechanism means that they can also relax the sphincter in the lower oesophagus, allowing reflux and triggering GORD. If lifestyle measures don’t help, talk to your GP.

Steroid tablets can cause indigestion and ulcers. Some ulcers burn through the wall of the gut or stomach, causing bleeding or even allowing the contents of the gastrointestinal tract to enter the abdomen. However, relatively few people develop these serious side effects. Conn and Poynard reported that three people in 1,000 (0.3 per cent) developed a peptic ulcer (one that hasn’t burnt all the way through the wall) while taking an inactive placebo. Oral corticosteroids increased the proportion to 0.4 per cent. In other words, one extra person taking oral steroids developed peptic ulcers for every 1,000 treated. So, if you develop heartburn while taking oral steroids, see your doctor or asthma nurse.

Indoor and outdoor pollution

The World Health Organization (WHO) estimates that outdoor and indoor pollution causes approximately two million premature deaths worldwide per year. Pollution from traffic and factories probably doesn’t cause asthma. However, pollution can trigger asthma exacerbations, partly by enhancing the effect of allergens.

While most people think of pollution as the toxic cocktail belching from cars, lorries and factories, we’re also exposed to pollution inside our homes, such as smoke from tobacco and (if you use them) coal or wood for heating and cooking. Indoor pollution can also contribute to poor asthma control. After all, we spend at least 75 per cent of our time indoors.


Tobacco smoke is probably the most important indoor pollutant for people with asthma. You don’t even need to be a tobacco addict to suffer. Passive smoking accounts for around one in every 100 deaths worldwide, according to The Lancet. Indeed, passive smoking in the home kills around 11,000 people every year in the UK alone, through lung cancer, stroke and heart disease. Passive smoking can also trigger bronchoconstriction and exacerbate asthma. Second-hand smoke caused 36,900 deaths worldwide from asthma during 2004, The Lancet reported. Active smoking, of course, poses an even greater hazard:

  • People with asthma who smoke regularly tend to endure more severe symptoms, have a worse quality of life, make more trips to A&E departments and are more likely to need hospitalization than asthmatics who do not smoke.
  • Smoking accelerates the decline in lung function compared with people with asthma who do not smoke. Indeed, FEV1 (a measure of lung function) can decline more rapidly in non-allergic cigarette smokers than among people with allergic asthma. On the other hand, quitting smoking can reduce the age-related decline in FEV1 to that typical among lifelong non-smokers.
  • Smokers are more susceptible than non-smokers to infections with rhinoviruses – a group of around 100 viruses that frequently cause common colds – partly because chemicals in tobacco seem to suppress the immune system. So the virus replicates more readily in smoke-damaged than in healthy cells in the lungs. The smoke-damaged cells are more likely to die during the infection. • Smoking tobacco or marijuana can cause symptoms similar to asthma, which can complicate diagnosis.
Smoking in pregnancy

Mums-to-be who smoke are more likely than those who don’t to experience problems during pregnancy, including miscarriage, premature birth, stillbirth, low birth weight babies and sudden infant death syndrome. Indeed, smoking during pregnancy increases infant mortality by around 40 per cent. Furthermore, children exposed to tobacco smoke while in the womb are more likely to experience serious respiratory infections (e.g. bronchitis and pneumonia), Otitis media (glue ear) and other ear, nose and throat ailments, psychological and behaviour problems and asthma as they grow up.

So the sooner you quit smoking, the better for you and your baby. The intense medical and social pressure against tobacco use in pregnancy makes some women reluctant to admit they smoke. However, for the sake of your baby and yourself, you need help. Your midwife or doctor should be able to offer you advice and support to quit. You could also call the NHS Pregnancy Smoking Helpline number: 0800 169 9 169.

Outdoor pollution

During the London smog in the winter of 1952, a mixture of fog, smoke and chemical fumes hung so thickly in the air that people could barely see a few yards in front of their faces. The smog claimed at least 3,000 to 4,000 lives in addition to those normally expected at that time of the year. Depending on how many people died because of the smog in the early months of 1953, the pollution could have killed as many as 12,000 people, Bell and colleagues estimate. The public outcry led to the 1956 Clean Air Act.

Air quality in the UK has improved over the last 60 years – at the same time as the number of people with asthma has risen. So, rather than causing asthma, air pollution tends to exacerbating existing respiratory diseases. For example, people living in towns and cities seem to be more likely to develop asthma due to pollen than those in the country. In part, townies are at increased risk because pollution exacerbates pollen’s ability to trigger an immune reaction.

Pollution is a complex cocktail of chemicals, which complicates analysis of the biological effects. Nevertheless, we know that many pollutants, alone or in combination, potentially exacerbate asthma. For example:

  • Nitrogen dioxide – a gas produced by cars, gas cookers or heating and power stations – irritates the lining of the lungs and nose.
  • Sulphur dioxide – produced by power stations, diesel engines and coal fires – caused most of the respiratory problems during the 1952 smog. Sulphur dioxide can trigger bronchoconstriction.
  • Ozone forms when sunlight reacts with nitrogen dioxide and some other pollutants. High ozone levels can cause breathing problems, trigger asthma and reduce lung function.

Many weather forecasts now predict the level of air pollution. When air pollution is high, people with asthma could experience discomfort or symptoms, so they should spend less time outdoors. It’s also a good idea to avoid exercising in front of an open window. Pollution levels are also much higher in other parts of the world than in the UK; it might be worth checking the air quality of any city you plan to visit before you decide whether to book your tickets.

Indoor pollution

With cars and lorries belching out toxic fumes, it’s easy to forget the risks posed by indoor air pollution. But most of us spend far more time indoors than outside, so our cumulative exposure to indoor pollution is greater. Again, several sources of indoor pollution can exacerbate asthma:

  • Levels of nitrogen dioxide produced by gas cookers and kerosene heaters inside the house can be higher than those produced outside by cars and power stations.
  • Open fires and paraffin stoves can produce high levels of sulphur dioxide and particulate pollutants.
  • Particulate matter released during cooking and by aerosols can reduce lung function and increase the risk of heart and lung diseases. Stir-frying, for example, creates a high concentration of particulate matter, including superheated oil particles.
  • Numerous sources – including some DIY products, cleaning products, air fresheners, paints and electrical goods – release natural and synthetic volatile organic compounds (such as formaldehyde). These may irritate the respiratory tract and possibly exacerbate asthma. Volatile organic compounds also react with ozone (produced indoors by some printers). The reaction generates other compounds that potentially undermine lung function.


On 6 and 7 July 1983, doctors in Birmingham treated 26 emergency cases of asthma over 36 hours, compared to the expected two or three a day. On 24 June 1994, A&E departments across London and southwest England managed 640 people with asthma and other respiratory diseases over 30 hours, almost ten times the expected number. On both occasions, D’Amato and colleagues comment, heavy thunderstorms swept the areas.

Since then, doctors as far away as Italy and Australia have reported a surge in the number of asthma cases during thunderstorms. D’Amato and colleagues suggest that thunderstorms concentrate pollen at ground level. The atmospheric conditions then cause the pollen to burst, producing aerosols of highly allergenic particles that – because of their small size – penetrate deep into the lower airways. In sensitive people, the high concentration of allergen triggers asthma. Indeed, people with allergic rhinitis caused by pollen (‘hay fever’) who do not normally experience respiratory symptoms can suffer full-blown asthma attacks during some thunderstorms. (Remember that, in effect, the respiratory tract is a single organ running from the nose to the alveoli.)

Thunderstorm-asthma seems to be rare. But the weather can affect the risk of suffering asthma and other allergies in other ways.

  • We’ve already seen that cold air commonly triggers asthma.
  • Ozone levels rise on sunny days, and this, as we’ve seen, can trigger asthma.
  • Certain weather patterns increase pollen release. Most flowers release pollen in the early morning, often triggered by changes in humidity. On the other hand, rain can remove pollen from the air.

So, if you think a particular weather pattern exacerbates your symptoms, try to limit your exposure at these times.

Finally, climate change may alter the long-term profile of allergens. For instance, American researchers have noted a rise in levels of ragweed pollen, fungal spores and poison ivy in recent years, which they attribute to rising levels of carbon dioxide in the atmosphere. The rise in carbon dioxide levels feeds the plant, which may prompt increased pollen production. The increased plant activity also offers fungi living on the leaves the opportunity to reproduce more rapidly and increase spore production.

Inside the house, climate change can increase humidity, which may encourage the proliferation of dust mite and mould. High temperature and humidity also speeds the decomposition of food, which is a feast for certain insects, some of which can trigger asthma in sensitive people. Cockroaches, for example, are a particularly common asthma trigger in the USA and some parts of Europe. (So avoid piles of papers and keep food in airtight containers to help control cockroaches.)

Poor adherence

The most effective drug is useless unless you take it correctly. That sounds obvious. Yet Clatworthy and colleagues found that, in the UK, a third of adults with asthma admitted poor adherence with their treatment. (The terms ‘poor compliance’ or ‘poor concordance’ also describe patients who don’t take their medicines as agreed with their doctor or nurse.) In another study, Bozek and Jarzab found that only between 9 and 21 per cent of patients aged 65 to 102 years with chronic asthma adhered well to their therapy.

There are a variety of reasons people with asthma may not adhere to medicines that could save their life. Some may deny that they are ill, disbelieve the diagnosis, have low expectations of treatment, suffer from psychiatric problems or fail to appreciate the risks associated with poor compliance. Others may comply poorly because they are worried about side effects or because treatment disrupts their lifestyle unacceptably. If this sounds like you, have an open and honest discussion about your concerns with your GP or asthma nurse.

Some people also take excessive amounts of their drugs – perhaps overdosing on steroid or bronchodilator – usually through fear that they’ll suffer a serious attack. Again, a full and frank discussion with your doctor or nurse should help you place the risks in perspective. In such cases, a self-management plan will often help to put you back in control and allow you to increase the dose of medication when your symptoms or peak flow worsen.

Often, however, poor adherence is unintentional. People may misunderstand treatment instructions, become confused over their medicines – especially if they suffer from other diseases and need to take several drugs – or simply forget. In these cases, adherence aids (such as a box that allows you to organize your tablets day by day) could help, as could simplifying your treatment and asking your doctor to check that you really need all the drugs. You could try keeping your steroid by your bedside if you need to take your anti-inflammatory twice a day. (Obviously, keep all medicines out of the reach of children.) The more drugs you need, the more the chance of poor compliance rises and these aids can help you remember to take your treatment on time.

People with physical disabilities may experience difficulties opening packaging or swallowing medication. Pharmacists may be able to suggest alternative packaging or dosing forms that overcome these limitations, such as avoiding ‘child-resistant’ pill bottles or using liquid formulations. If you can’t use the inhaler correctly, changing the inhaler or using an aid may help.

Finally, other family members and caregivers should understand the cause of and triggers for asthma, as well as the need for effective treatment, especially, for example, if the person is elderly or tends to forget his or her medication. Unintentional poor adherence may become increasingly common with advancing age or in those suffering diseases, such as dementia, that compromise their mental abilities. In such cases, involving family members and other caregivers promotes adherence.

Pregnancy and asthma

The British Guideline for Asthma Management (which we’ll discuss further in Chapter 6; see Useful addresses) notes that poorly controlled asthma increases the risk of numerous complications for the baby and the mother, including:

  • hyperemesis (sickness, especially in the morning);
  • pre-eclampsia (dangerously raised blood pressure – hypertension – during pregnancy);
  • vaginal haemorrhage;
  • complications during labour;
  • foetal growth restriction (poor growth of the developing baby) – in one study, suffering asthma symptoms daily increased the risk of poor foetal growth by 125 per cent;
  • low birth weight – one study found that suffering asthma exacerbations during pregnancy increased the risk of low birth weight by 154 per cent;
  • premature birth;
  • increased risk of death immediately before and just after birth (the perinatal period);
  • neonatal hypoxia (lack of oxygen to the baby), which can cause cerebral palsy, blindness and epilepsy as well as impairing mental and psychomotor development.

This is a worrying list. But it’s important to remember that most women with asthma have normal pregnancies and, provided their symptoms are well controlled, the risk of complications is small, the British Guideline on Asthma Management notes. Indeed, asthma often improves during pregnancy.

Obviously, the mother’s body undergoes numerous, often profound, changes during pregnancy, some of which could worsen or improve asthma. One study found that asthma worsened during pregnancy in 35 per cent of women. Another study found that asthma improved and deteriorated in 23 and 30 per cent respectively. So, broadly, asthma improves in one-third of women during pregnancy; a third of mums-to-be finds that their asthma symptoms worsen; and symptoms don’t change in the final third of expectant mothers.

Severe asthma is more likely to worsen during pregnancy than mild asthma. Nevertheless, symptoms may improve during pregnancy in some women with serious symptoms and deteriorate in some with mild asthma. Asthma is also most likely to worsen during the second and third trimesters, with the risk reaching a peak during the sixth month. The risk of suffering an exacerbation appears to be lowest during the last month of pregnancy. But changes can emerge almost any time during the nine months.

Short-acting bronchodilators (relievers) control most exacerbations during pregnancy. Nevertheless, 11 to 18 per cent of expectant mothers with asthma will suffer at least one exacerbation during their pregnancy that needs treatment in an A&E department. Of these, 62 per cent will require hospitalization. This unpredictability and the risks to you and your baby mean that it is especially important to monitor your peak flow and symptoms during pregnancy.

Breast-feeding and asthma

Breast-feeding may lower a child’s risk of suffering from asthma, partly by reducing exposure to food allergens in early infancy. Indeed, breast-feeding seems to reduce the risk that infants will develop asthma, regardless of whether one or both parents suffered from allergies. Nevertheless, breast-feeding’s protective effect is most marked in high-risk infants (for example, because their parents suffered from severe allergies). However, mothers need to breast-feed the baby for at least four months to gain the maximum protection.

Menstrual cycles and asthma

Many women find that their asthma symptoms worsen just before their period. Estimates vary from study to study, depending partly on the definitions used. Some researchers suggest that up to 40 per cent of women experience premenopausal asthma. Murphy and Gibson found that 57 per cent of women showed premenstrual increases in symptoms and asthma medication use. However, only 25 per cent experienced premenstrual exacerbations in each of the cycles studied. Dratva and co-researchers found that women were 2.3 times more likely to show increased bronchial hyper-reactivity in the three days before and the same time after the first day of menstruation, compared to other times in their cycle. So premenstrual asthma is certainly common.

As you might expect, changes in hormone levels underlie these premenopausal exacerbations, which do not seem to depend on whether or not the woman suffers from allergic or intrinsic asthma, and there is no clear link with symptom severity. Levels of the sex hormones oestrogen and progesterone during the menstrual cycle seem to increase bronchial reactivity, partly by altering the activity of beta2-receptors (responsible for controlling airway calibre) and possibly by increasing levels of leukotrienes, an inflammatory mediator. Oestrogen may also reduce the body’s production of natural anti-inflammatory chemicals.

Asthmatic worsening before the period appears to be associated with other aspects of the premenstrual syndrome. Pereira-Vega and colleagues found that 45 per cent of women reported a premenstrual worsening of respiratory symptoms, peak flow or both. These women were also more likely to report premenstrual dysphoria (feelings such as anxiety, depression, fatigue, irritability and mood swings) and sensations of swelling or tension in their abdomen, breasts and elsewhere. This supports the idea that hormonal changes cause premenstrual exacerbations.

Inhaled steroids may be less effective against perimenstrual asthma worsenings (those around the period) than in other exacerbations. As rising leukotriene levels may contribute to premenstrual asthma, Dean argues that adding a drug that specifically blocks these mediators – a leukotriene receptor antagonist  – might be a better treatment choice than increasing the steroid dose. Some (but not all) studies suggest that oral contraceptives lessen the increase in bronchial hyper-reactivity around the time of your period and protect against premenstrual asthma. You could try keeping a diary recording your periods and peak flow as well as asthmatic and perimenstrual symptoms. If this reveals a worsening around the time of your period, discuss your treatment choices with your doctor or asthma nurse.

Asthma and the menopause

Some women develop asthma for the first time after their menopause, especially if they are overweight. And the risk of developing asthma in postmenopausal women rises the more pounds they pile on. Furthermore, some forms of hormone replacement therapy (HRT) may trigger asthma. (This isn’t surprising – we’ve already seen that hormonal changes probably underlie menstrual asthma.) For example, Romieu and colleagues found that using HRT containing oestrogen alone or oestrogen plus progestin (a synthetic progestogen) doubled the risk of developing asthma. However, another study found that only those who used HRT containing oestrogen alone were at increased risk (a 54 per cent rise), particularly if they had never smoked (80 per cent rise) or suffered allergic disease before asthma’s onset (86 per cent increase).

The differences between the studies suggest that HRT’s effects on asthma vary in different subgroups of women. If you feel that you need HRT, for example to treat hot flushes, night sweats, vaginal symptoms and cystitis, you may want to discuss the potential impact on your asthma with your GP. In some cases, there may be alternative ways to manage your symptoms.

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