Sometimes a simple problem produces truly alarming symptoms. Molly, who is an 18-month-old brindle boxer, spent an exuberant sunny afternoon last week playing in the garden and around the pond, and then came in to the house when her owner called her for tea.

When she came in her eyes, more precisely her eyelids, looked slightly swollen. Within half an hour her whole face was swollen, especially her lips and eyelids, and her body was covered all over with large blotches about the size of a £2 coin.

Her frantically worried owner could see these getting bigger before her eyes, the hair on each one standing up like a badly-cleaned paintbrush. Every so often she lifted her paw and rubbed her face. A look around the garden did not show up anything out of the ordinary.

A few minutes later her owner phoned me. Although uncomfortable, Molly was breathing fine so I asked them to bring her along to the surgery as soon as she could. When they arrived the lumps were no bigger, in fact they were, if anything, starting to fade.

She was still uncomfortable and her lips and eyelids were two or three times their normal thickness and had a velvety feel to them.

Molly's temperature was normal. She sat in a miserable and uncomfortable heap very different to her usual bouncy self. I explained that the symptoms were caused by an allergic reaction that had caused histamine to be released in the skin.

The substance that causes the reaction can vary quite widely. Insect bites and stings and plants that the dog either rubs against or chews are the commonest offenders, but occasionally a food or even a medicine can cause the same effect. Although there was no way of knowing the precise cause this did not stop me treating Molly. I gave her an injection to stop the allergy and within three hours the symptoms were disappearing rapidly.

Nearly all the cases like Molly that I see happen in the late summer and nearly always the dog has had access to plants and insects outside. Though painful and alarming these attacks are only dangerous if they cause breathing difficulties, though they can take several days to go completely. Most often it is short-haired dogs who are affected which would fit with a plant that rubs against the skin causing the problem, like stinging nettles.

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.