The word "allergy" is bandied about all too often, not least by me, when a miserable eight months of unexplained nose-blowing turned me into a monstrous medical-trivia obsessive. Plagued by sleeplessness, my addiction to medical websites spiralled. These advised pulling up carpets; replacing duvets and pillows; moving to an area without trees; spending my summers indoors with the windows closed.

But summer passed and nothing changed. By winter, Net Doctor had been added to my internet favourites. I latched on to the notion that nasal polyps were to blame. "The most effective treatment is surgical removal," said one website. "There is the risk of bleeding from the nose or a black eye." And piercing of the brain. That's the thing about medical websites: before you know it, you're virtually dying.

It was time to get my facts straight, so I went to Allergy UK, the leading medical charity in the field. Their website recommended a skin prick test, by a bona fide medical practitioner, and suggested the London Allergy Clinic.

And so it was that the kindly consultant, Lawrence Youlten, began tucking microscopic particles of dust mites, tree and grass pollen, cat and dog hair, and mould spores under the skin on my forearm to see if I developed itchy, red weals, which would indicate an allergic reaction.

According to Youlten, only about a third of the population suffers from allergies. "If your parents haven't passed on the genes for being atopic [allergy-prone], then you're unlikely to develop an allergy. The typical atopic child would have eczema when they're young, would be a snuffly child who developed a pet allergy or hay fever, and would then be in the running for asthma as they got older. So that's the package - though not everyone has it all."

There is evidence, however, to suggest that an element of nurture in the development of allergies. "The first child in the family tends to be more allergy-prone," says Youlten. "The theory is that your immune system is very versatile, and if, during the first year of your life, you're the only child in the family and protected, and you don't have infections, the immune system thinks, 'What can I do to make myself useful?' and starts attacking things like pollen and cat hair."

There were no allergic weals on my forearm. As you would expect with the youngest of three children, who grew up in a veritable menagerie of pets, I do not have an allergy. One can have the symptoms, it seems, without having the allergy. The correct word to bandy about is "rhinitis", which describes inflammation of the nasal lining, often affecting the sinuses and middle ear. Rhinitis as in rhinoceros. As in big, red, angry, runny nose. Rhinitis can be caused by all sorts of things, for example a nasty cold or infection. And it doesn't go away when summer's over. The good news for rhinitis sufferers is that nasal steroids not only treat symptoms, they hasten the natural repair of the nasal lining. And at least there's still a word to put into the medical search engines.

· The London Allergy Clinic, 66 New Cavendish Street, London W1, 020-7637 9711. Allergy UK: 020-8303 8583 (allergyfoundation.com).