With Dr Bisola Laguda, Associate Specialist in Paediatric Dermatology, Great Ormond Street Hospital

Spots can make life miserable for teenagers. Think back to when you were in your teens. You may remember how uncomfortable and embarrassing it was to have spots at this sensitive age.

As many as 85 per cent of 12 to 25 year olds develop spots, and boys and girls are equally affected and up to 15 per cent seek medical treatment for their condition. They are right to do so. If left untreated persistent spots, or acne, can result in life-long scarring.

But modern treatment is very effective and should mean scarring is a thing of the past. It’s really important to seek and start treatment early, and minimise the chances of scars developing.

What is acne? It’s basically a very common skin condition that affects the sebaceous glands in the skin, found mainly on the face, chest and back, and hair follicles.

The glands produce oil to carry cells, shed by the sebaceous glands, through ducts to the surface of the skin. Too much oil blocks the openings of the ducts, which allows waste cells to accumulate under the skin’s surface forming a plug.

If the plug stays below the surface, it is light in colour and is called a whitehead. If it enlarges or pops out, the tip is dark and forms a blackhead. Red lumps and yellow spots occur when the skin is inflamed. Teenagers with black skin often find that spots make their skin darker, and this pigmentation can last for many months.

Spots usually appear around the onset of puberty and reach their peak between 17 and 21. They are not infectious or contagious.

What causes it? Forget stories of greasy food or poor hygiene, acne is caused by over-production of oil from the sebaceous glands. These glands are controlled by sex hormones which flood the body during puberty. It isn’t over production of sex hormones that usually causes the problem, but the sebaceous glands responding excessively to normal hormone levels.

Bacteria also play a part. During puberty many types of bacteria are normally present on the surface of the skin. When certain bacteria come into contact with excess oil, they enter the ducts of the sebaceous glands where they produce chemicals, which can escape into deeper parts of the skin. In severe acne this can cause big tender spots called nodules, which can last for months and leave scars.

There can be aggravating factors. Teenage girls often report a flare-up of spots just before menstruation.

Stress and certain foods, such as fast food and chocolate, seem to make acne worse although there is no scientific evidence to prove this. Some cosmetics may also provoke spots, especially those that contain oils, fatty acids and waxes.