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Causes of acne
Most people develop acne during adolescence. It is most prevalent in those aged 16 to 18 years. The reasons are:
- There are higher levels of sex hormones at puberty than in younger children.
- These hormones are converted in the skin to dihydrotestosterone (DHT) which stimulates oil glands to enlarge.
- The oil glands, called sebaceous glands, produce sebum. The more sebum, the more likely it is that acne will be troublesome.
- If sebum and keratin (dead skin cells) block the skin pores, comedones can develop.
- The wall of the follicles may rupture.
- Bacteria and comedonal debris cause acne pimples or pustules (inflammatory lesions).
Acne usually becomes less of a problem after the age of 25 years, although about 15% of women and 5% of men continue to have acne as adults.
Aggravating factors
Some people have particularly severe acne. This may be because of:
- Genetic factors (family members have bad acne)
-
Hormonal factors (higher levels of androgenic hormones) due to:
- Polycystic ovaries (common)
- Enzyme deficiency eg sterol hydroxylase deficiency (very rare)
- Excessive corticosteroids (eg Cushing's disease) (rare)
- Psychological stress and depression
-
Environmental factors such as:
- High humidity causing swelling of the skin
- Cosmetics especially certain moisturisers, foundation and pomades (watch out for lanolin, petrolatum, vegetable oils, butyl stearate, lauryl alcohol and oleic acid)
- Petroleum oils
- Pressure from headbands & chin straps (eg: "fiddler's neck")
- Dietary factors such as excessive dairy products (controversial). A study published in 2007 in male adults with acne has shown benefits from a low glycaemic diet.
- Certain medications.
Why acne eventually resolves is not understood. It does not coincide with a reduction in sebum production or with a reduction in the number of bacteria. It may relate to changes in the sebaceous glands themselves.