For five days our two-year-old daughter has had mouth ulcers. She saw the GP, who prescribed some penicillin and a steroid paste to put on the ulcers. She had one dose of penicillin, but has refused to take it since then. Does it matter that she started a course of penicillin and didn't finish it?

Dr Fred Kavalier answers your health question:

Most mouth ulcers in young children are caused by virus infections. A common cause is herpes simplex, the same virus that causes cold sores. The first time a child comes into contact with the herpes simplex virus, it can cause a painful crop of ulcers in the mouth, often associated with swollen glands under the jaw. These will heal up naturally, but it may take up to a week, and it can be very painful. There are other causes of mouth ulcers in children, including the virus that causes hand, foot and mouth disease. The penicillin was probably the wrong treatment, and it doesn't matter that your daughter started a course and didn't finish it.

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