Even before a spot appears things will be happening below the surface of the skin. For example you may feel a slight tenderness, soreness or pain in the area of the skin before the spot appears. However it is fairly common for a spot to appear overnight. The type most likely to take time to appear is the larger red spots (papules/cysts); these may take a few days to enlarge and a few weeks to fade. Small pustules (yellow coloured) are the type most likely to appear quickly, sometimes within hours.
Understanding the different stages of a spot may help to reinforce the need to use anti-acne medications, even when there are no visible spots. These work by attacking the causes of the acne before they appear and are the best chance of keeping it under control.
Papule (red spot)
The very beginning of a papule may take place up to three or four days before it is seen. The build up of oil in the hair follicle will begin to mix with dead skin cells that make it sticky and viscous. The blockage leads to the start of an inflammatory response. At this stage acne treatments would be able to fight inflammation and target the P. acnes bacteria, reducing the chances of it progressing to stage 2
The inflammation will mow cause an area of redness and swelling, reaching the surface and becoming visible. This may occur two to five days from the first stage.
The papule enlarges as inflammatory responses increase its size and tenderness. After this, the spot will begin to die down and become a macule (a healing red spot). Stage 3 may last up to three weeks, although the average is seven days. Stage 4 The skin is recovered. Some minor scarring may remain.
Comedone (blackhead, whitehead)
The build-up of dead skin cells in the hair follicle becomes trapped in the oil , as in a papule, but fails to attract the cells responsible for causing inflammation. This build up may take several weeks
If the blockage reaches the skin surface it will turn black. Blackheads may last several weeks, months or even years if left untouched. The blockages that do not reach the surface and sit in the follicle (a closed comedone) may be very hard to notice with the naked eye; they are the type that is more likely to trigger an inflammatory response and lead to a papule. Research suggests that 25% of closed comedones may resolve in three to four days, with 75% developing into inflamed lesions.
If an open comedone is extracted, the pore may close over a period of a few days. However some comedones may leave behind an enlarged pore due to being stretched by the solid plug of the sebum.
Pustule (yellow spot)
Inflammatory responses in the hair follicle may be much faster than in a papule. It is difficult to estimate how long it may take the pustule to form, as this will depend on the size and depth of the inflamed area. If the inflammation is close to the surface of the skin, some pustules may appear within 10-12 hours
If left untouched, pustules can heal into a macule within five days. Deeper pustules may last for up to two to six weeks before healing.