"Normally the season starts much earlier," Professor Roy Kennedy, director of the unit, tells us. "There's a succession of pollen starting with birch, which runs into other tree species, so they all come one after another.
"But because everything's been held back so long, all these things are potentially occurring at the same time."
Professor Kennedy says people with hayfever have been let off lightly from pollen so far this year: "It's been unusually cold, so there's been no activity at all in the earlier part of the year, in March and before that.
"It's had the tendency to compound all these episodes from each tree species so they occur at the same time, and potentially shunt those further back so they occur when also grass pollen is beginning to break out as well.
"So you've got this mixture of things occurring rather than having them one after another."
Double allergy trouble?
If someone is already having allergies triggered by one type of pollen, what happens when there is another one in the air which affects them?
"Most people are only sensitised to one pollen," Professor Kennedy says. "But there is part of the population that are sensitised to more than one allergy or one pollen."
Those people, he says "could potentially suffer more adverse effects when all the pollens are occurring together."
Bucking the trend
Last year, warm weather in early spring meant an unseasonably early start to the hayfever season, continuing a trend towards earlier and earlier hayfever and allergy symptoms, until now. "This kind of season  hasn't been seen for a long time," Professor Kennedy says. "Normally, over the last 20 years, we are starting earlier.
"It may have been cold in previous years, but I'm talking about unusually cold, with frosts night after night and very cold conditions, 1-3C during the day."
To avoid the extra pollen, Professor Kennedy says one solution may be to follow the pollen forecast and try to avoid going outdoors: "Normally you see a peak in pollen during the daytime period. So if you stay indoors that time, you're unlikely to experience the peak of the pollen around noon time, although peaks can occur at other times."
He admits staying indoors isn’t always practical, but other precautions or medication may help, as well as watching out for the specific type of pollen that sets off your allergies.
"Your sensitisation is related to the amount of pollen that you are exposed to."
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