At this month's Winter Olympics, as many as half of the competitors will be sufferers of exercise-induced asthma, according to a study by Yale University. An unfortunate ailment for any athlete – but at least they're not allergic to snow. A surprising number of athletes have allergies to key components of their sport. In the early noughties, tennis player Lleyton Hewitt, above, suffered from a mystery energy-sapping illness that was eventually diagnosed as an allergy to grass (no wonder, Hewitt joked, he lost in the first round of Wimbledon 2003).

Hewitt, at least, could spend most of the year playing on hard courts or clay; pity golf pros like Jesper Parnevik, left, and Jill McGill, both of whom share Hewitt's allergy. Parnevik teed off at the 1999 Open with tissue paper stuffed up each nostril, a tactic he might have borrowed from McGill at a Florida tournament in 1995. She said: "Every time I bent over the ball fluid came rushing out of my nose. I had no choice but to staunch the flow."

Ugandan steeplechaser Dorcus Inzikuru – allergic to "extreme weather" – finished a 2005 race in sunny Doha bleeding profusely from the nose. Cyclist David Millar, allergic to the sun ( "pretty inconvenient as a cyclist"), races slathered so thickly in sun block that he resembles a corpse.

Jade Johnson, right, continues to long jump despite an allergy to sand, Ian Thorpe overcame a childhood allergy to chlorine to become an Olympic swimming great, and Andy Townsend led Ireland at USA '94 despite developing an allergy to the bug repellant sprayed on to the World Cup pitches.

American football player Kermit Tyler, meanwhile, was diagnosed with the cruellest condition of all. Allergic to "strenuous exercise" – a freak but legitimate complaint – Tyler's career was over in 2008 at the age of 19.