Threadworms: Preventing them spreading

My six-year-old son may have threadworms, as he has been scratching a lot. A friend told me to get mebendazole. How can I ensure that our other two children don't catch them too?

Dr Fred Kavalier answers your health question:

Threadworms look like small pieces of thread. They live happily in the intestine of humans. At night, they venture out on to the skin around the anus to lay their eggs, which causes it to become intensely itchy. If you scratch it's hard to resist the eggs get on to your hands and under your fingernails. Children like to lick their fingers, and this allows the eggs the re-enter the body, and so the cycle goes on. Three things help to break the life cycle of threadworms: wearing pants in bed (to prevent the eggs from getting on to the fingers); washing hands and scrubbing fingernails with a brush several times a day, particularly after going to the toilet; and treating the whole family with mebendazole (also known as Vermox, and available from chemists) to kill any threadworms living in the intestine.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.