Acne is the hallmark of adolescence : the term comes from the Greek for the “an eruption of the face,” and although acne may sometimes persist, most people find that the condition fades away by their early 20s. Before puberty most children have unblemished skins, but the surge of sex hormones in adolescence has dramatic effects. The most obvious is the growth of hair in the armpits and genital areas in both sexes and on the face of boys. The same hormones increase the size and number of glands in the skin (called sebaceous glands) that produce a greasy substance called sebum to lubricate the hairs.

In adolescence, then, the sebaceous glands become bigger and more active, and the sebum they produce often becomes thicker. In addition to making the face greasy, this thick sebum may become trapped within some of the glands by a plug of skin debris and hardened sebum. The plug or block is easily visible as white – or darker –colored spots the size of a pin: whiteheads and blackheads. If the blocked gland becomes infected, it will become inflamed, red, and sore. These raised red pimples may be quite small, but sometimes one becomes very inflamed and turns into a really painful boil. Someone who suffers from bad acne for several years may eventually have large numbers of scars from old inflamed spots. These spots, and the scars they may leave, are most obvious on the face, neck, and shoulders, where there are large numbers of sebaceous glands.

Several factors make acne worse; jobs that involve oil getting on the skin or that cause a lot of sweating are well-known factors (such as working in a hot and steamy environment). Other aggravating factors include some prescribed drugs such as steroids. The oral contraceptive pill may make acne worse, but sometimes makes it better. Experts disagree about whether diet makes any difference: some recommend a low-fat diet and the avoidance of chocolate and carbonated drinks, while others say that diet has no effect at all. Certainly masturbation has no effect on acne. Sunlight in moderation may help.

The first line of treatment is to soften and remove the grease, and every pharmacy has a wide choice of acne lotions that are probably cheaper and easier to get than a similar lotion prescribed by a doctor. Often this is all that is needed. If lotions don’t work, you’ll need to see your doctor because the next stop is to get rid of the bacteria that make the pimples inflamed. This requires treatment with a safe, simple antibiotic (usually tetracycline) for about four to six months. If symptoms persist, then young women may be recommended hormone treatment to block the effects of the androgens (the male hormones). The hormone preparation used also acts as a contraceptive.

If none of these treatments works, then the final weapon is a synthetic variant of vitamin A, isotretinoin. This reduces the size of the sebaceous glands by about 90 percent, it makes the skin much less oily, and it discourages inflammation. Why isn’t it the first-line treatment? Partly because it is very expensive and partly because it is powerful stuff. If a woman is taking isotretinoin, she must not get pregnant since it causes serious fetal deformation. Acne is now curable, and indeed surveys of schoolchildren have shown that severe acne has become very rare.

Your appearance at the age of 13 or 14 is little guide to how you will look at 20, let alone at 25.