'I've never had it before," says a colleague. "Now I'm getting through a box of tissues a day."

I know how she feels. Normally an antihistamine sees off my mild hay fever but this year my eyes are red and streaming, and my nose feels the size of an orange. And we're not alone.

What's going on? I call the National Pollen and Aerobiology Research Unit in Worcester. "It's the birch pollen season," says a spokeswoman. Birch pollen affects 25% of sufferers. Grass is the worst, affecting 95%, but the grass pollen season doesn't really get going until June. Odd, then, that we're all suffering now. "Last year, pollen levels were low," she says. "At the moment it's good weather for pollen release, but it's nothing out of the ordinary."

Unconvinced, I ring the Department for the Environment. Could it be pollution? "Hmm ... we haven't put out our first smog warning yet this year," says a spokesman. "Generally speaking, air quality has been improving over the last 10 years."

I need an expert. I call University College London. "Yes, we've noticed that it's a lot worse," says the press officer there. "Even people who have never had it before are suffering." Now I'm getting somewhere.

She puts me in touch with immunologist Professor Graham Rook: "I'd be surprised if anything was making you worse this specific year," he says. But he goes on to explain the so-called "hygiene hypothesis", suggesting that people's allergies have got worse because we no longer get enough exposure to dirt. In the 19th century, he says, farm workers rarely suffered from hay fever. "Sophisticated townies were more likely to get it. Summer sneezing was a sign of culture."

So there it is. Perhaps I'm just too sophisticated. Now, excuse me while I have a sneezing fit.