Millions of hay fever sufferers could be facing a particularly bad summer - because of the cold spring.
Usually, there is a gradual release of pollen, but this has been delayed by the chilly weather.
Different pollen bursts are now expected to happen at the same time, with the highest pollen levels in 50 years predicted.
"Hay fever sufferers could be badly affected," warns the National Pollen and Aerobiology Research Unit.
Hay fever is a common allergic reaction to pollen, a fine powder released by plants.
It affects 1 in 5 people at some point in their life and can cause sneezing, running noses and itchy eyes.