Why is my hay fever so bad? By the Met Office’s Aidan McGivern
It starts early in the morning with a scratchy throat and itchy eyes. By lunchtime, the sneezing begins, soon followed by a runny nose. Friends and colleagues ask if I have a cold. I wish – at least head colds end after a few days. I’ve had hay fever since I was a teenager. Some summers are worse than others. This summer has felt particularly severe – and I’m not alone.
Following a spring that lurched seemingly overnight from freezing to roasting, the highest levels of pollen for more than a decade have been observed across the UK’s pollen count monitoring network. Although there are 18 million hay fever sufferers in the UK, the impact of this year’s unusual levels will vary from person to person.
Pollen grains are extracted from the atmosphere in a ‘Burkard trap’, simply a piece of sticky tape surrounding a rotating drum. Individual pollen grains are identified under a microscope and counted by an expert observer.
The specific types of pollen grain spotted under the microscope varies significantly throughout the year. The tree pollen season begins in the middle of March and can last until the middle of May, whilst the grass pollen season typically runs from late May until the end of July. Halfway through the summer, various nettles, weeds and fungal spores start to blossom.
Alongside seasonal peaks and troughs, the weather plays an important role in varying levels day-to-day. Optimum weather for the release of grass pollen is warm sunshine with enough of a breeze to carry the pollen grains. Wet weather will temporarily supress pollen release but occasional bursts of rain are necessary to revive the supply.
Since pollen peaks during the morning, shortly after its release, the timing of any rainfall is crucial. A wet morning will help keep levels low all day, whilst an afternoon shower may cause less of an impact.
2018’s cold and wet March led to a delay in the start of the pollen season but when spring finally sprang, all of nature appeared to blossom at once. Instead of a gradual release of pollen, there was an explosion. By the end of spring, the sunniest May on record as well as consistently warm temperatures helped release huge amounts of grass pollen into the air we inhale.
High pollen levels are observed when there are 50 to 150 grass pollen grains in each cubic metre of air. We’ve seen even higher levels at times this year but not everyone has the same tolerances. Whilst many start sneezing only when pollen levels are high, others are sensitive even when levels are low.
Grass pollen is the most common cause of allergies, affecting 95% of hay fever sufferers. 20% of hay fever sufferers are affected by tree pollen with much fewer people affected by weed and other pollen species.
Knowing which type of pollen you or your child are allergic to may help you manage symptoms at different times of year, but it can be complicated. There are around 150 different species of grass in the UK that cause hay fever, with different people affected by different grass species.
A dedicated research programme, now two thirds of the way through, aims to identify the most significant of the 150 different species of grass pollen in the UK by using DNA sequencing and the UK plant database. Called PollerGEN the research involves the expertise of partners from Bangor University, Aberystwyth University, University of Exeter, University of Worcester, University of Sydney and the UK Met Office.
These findings could help hay fever sufferers in the future. For instance, you may know you are allergic to grass pollen, as opposed to tree pollen. But do you know which type of grass pollen you are allergic to? This information could lead to detailed and local warnings, including which pollen is affecting which area and in what concentrations.
Planners, developers and councils could go even further and use this insight to change our local environments. By replacing those grass species that cause most allergies in our sports fields, parks and neighbourhoods, fewer people may be affected.
A radical change, perhaps. But, if one day it helps relieve the symptoms of millions of hay fever sufferers it’s a change not to be sneezed at.