Q My son has an abscess at the root of a tooth. It is very painful, but the dentist will only give an antibiotic and not remove the tooth until after it is healed. Meanwhile he is in a lot of pain. Why won't he take the tooth out?

A Your dentist is quite right. The aim is to get the infection to die down before he treats the tooth. Then he may be able to save the tooth. And to try to remove it while it is infected risks complications, like spreading the infection into the bloodstream, to give septicaemia. It is much safer to use an antibiotic first.

Q What is the difference between irritable bowel and inflammatory bowel disease, which my doctor refers to as IBS? Are the two the same?

A No. Inflammatory bowel disease describes two main bowel disorders, ulcerative colitis and Crohn's disease. In both there are ulcers in the bowel wall, and there is diarrhoea with blood and mucus (like phlegm) in it. In irritable bowel the bowel wall is healthy: the problem is a form of cramps in the bowel muscle. That leads to pain and distension in the abdomen with wind and occasional bouts of 'rabbity' stools or constipation. There is no blood in the motion. The two forms of bowel disease are quite different, with very different treatments.

Q I have a fungal infection in the nail of my big toe. My doctor has given me a paint to put on it for two months. Why does it take so long to cure it?

A The nail grows very slowly, and it takes a long time for the treatment to penetrate into the nail deep enough and in enough concentration to kill the fungus. At least the modern treatments do work - in the past, once a nail was infected it remained so for the rest of your life.

Q I'm thinking of going to West Africa for a beach holiday. Is it really necessary to have a yellow fever vaccination? I hear that it is particularly sore, and that there is a very low risk of catching it.

A There was recent outbreak of yellow fever in Senegal (near the Gambia), with deaths numbering in the twenties. As there is no satisfactory treatment for yellow fever once you have caught it, I wouldn't go near West Africa without being immunised against it. The vaccine is no worse than any other immunisation.