S is for scarlet fever, an infectious disease usually affecting children, which is nowadays less frightening than it sounds. Caused by a genus of bacteria called Streptococcus, it is characterised by a sore throat, a fever, and a mass of tiny red spots on the neck and upper body, caused by a toxin released by the bacteria. The rash spreads rapidly, the face becomes flushed and a "strawberry tongue" - white coating with red spots - may develop.

A child with scarlet fever should have plenty of rest and fluids as well as paracetamol to reduce fever. Treatment with antibiotic drugs, usually penicillin, normally results in rapid recovery. There is a risk of rheumatic fever and kidney inflammation developing if the disease is not treated promptly.

T is for toxic shock syndrome (TSS), a lethal form of blood poisoning associated with the use of vaginal tampons which hit the headlines in the early Eighties, causing panic among millions of women. TSS is caused by a toxin produced by Staphylococcus aureus, a normally harmless bacterium. Symptoms include high fever, vomiting, a sunburn-like rash, diarrhoea, faintness, muscle aches and dizziness: any woman who develops them should get medical help immediately and remove any tampon she might beusing. Serious complications include shock, kidney and liver failure.

It is not known why some tampons, particularly ultra-absorbent ones, increase the risk of TSS. There are various, mostly unproven, theories that they trigger production of the toxin by changing the bacterial environment in the vagina, by "binding" magnesium or by increasing vaginal dryness. In the US, after the most super-absorbent tampon ever made, called Rely, was withdrawn from the market, levels of TSS fell dramatically.

TSS is rare, with about 40 cases diagnosed in Britain each year. Although about 70 per cent of cases occur in women using tampons, it can also develop from burns, boils, insect bites and surgery. It can be fatal, but if caught early enough it can be successfully treated with antibiotics. Women who wish to use tampons can reduce their chances of getting tampon- related TSS by:

using the lowest absorbency tampon suitable for their period flow: if the tampon is dry and difficult to remove, absorbency is too high;

washing hands before and after insertion and changing tampons regularly;

using sanitary towels occasionally;

never inserting two tampons at the same time;

ensuring that the last tampon used during a period is removed.

The Toxic Shock Syndrome Information Service, funded by leading tampon manufacturers, runs a telephone advice line: 0171-617 8040.

U is for urticaria, a skin condition more commonly known as nettle rash or hives. It results in the appearance of itchy weals - raised white or yellow lumps surrounded by an area of red inflammation - either on the trunk or limbs. The most common cause is an allergy in which the chemical histamine is released from skin cells. Urticaria is often caused by an allergic reaction to food - particularly eggs, shellfish, strawberries or nuts - food additives such as tartrazine, or a drug - penicillin or aspirin. Itching can be relieved by calamine lotion or antihistamine drugs, although more severe cases may require steroids. Identifying and avoiding the trigger factors can help to prevent future allergic reactions.

Neonatal urticaria occurs in newborn babies but usually clears up without treatment.