Hay fever sufferers have been forced to endure the longest hay fever season in more than two decades, scientists said.
The hay fever season for people who suffer from grass allergies, accounting for about 80% of sufferers, has been about three weeks longer than usual.
Pollen counts are usually high between the start of June and the middle of July but this year they started early and went on for longer.
Dr Catherine Pashley, who works in the infection, immunity and inflammation department of the University of Leicester, said this summer has been "distressing" for people with hay fever, as symptoms including itchy eyes and runny noses have lasted longer than they usually would.
Scientists working in the Midlands measured the first day of "high count" grass pollen on May 25.
The hay fever season usually begins a week later at the start of June. The last time the season started this early was in 1991 when the first high pollen count day was on May 24.
"Through our association with the charity Midlands Asthma and Allergy Research Association (MAARA), we have pollen data for this region going back to 1968," said Dr Pashley.
"Using this we can see that we have only had three years that it has been this early."
The last "very high" grass count this year was on July 22, Dr Pashley said. The last time a "very high" grass pollen count occurred this late in the season was on July 23, 1985.
She said: "The season started early and finished late. People with hay fever have suffered over a prolonged period."
Dr Pashley said the interchanging wet and dry weather has led to the prolonged season.
"We had warm wet weather in late spring, which was conducive to grass growing and producing pollen," she said.
"When the flowers are mature in the early summer months, release and dispersal of pollen depends on dry weather, with the ideal for a high count being a warm day with a light wind.
"Rainfall will usually result in sharp decrease in airborne levels of grass pollen. Grass florets will remain shut on dull or wet days, with the pollen being released during the next dry period.
"Our summer has been interspersed with lots of wet days and a few dry sunny days which has resulted in the season starting early, and continuing longer, but having lots of low pollen days within it."
Hay fever symptoms are likely to be worse if the pollen count is high, it is classed as high when more than 50 grains of pollen are found in every cubic metre of air. It is categorised as "very high" when 150 or more grains of pollen are measured in every cubic metre of air.