21st December 2011 - You check the pollen count, take your allergy medicine, and yet hayfever symptoms can be worse in spring than summer. Researchers in the Netherlands are trying to find out why.
Hayfever is also known as seasonal allergic rhinitis. The NHS says it affects one in five of us.Allergy UK says grass pollen is the most common allergen and is in the air from around May to July. The sneezy season runs from February to June for tree pollen and September and October for weeds.
Scientists in the Netherlands have found that regardless of medication and other allergies, for the same grass pollen levels, hayfever symptoms are worse in the first half of the season than later on. They report their findings in BioMed Central's journal Clinical and Translational Allergy.
For two seasons in 2007 and 2008, researchers looked at about 80 people with hayfever who lived around Leiden, and compared the pollen counts with their daily symptoms.
The participants were also tested for other common allergies including birch pollen, house dust mites and pet triggers from dogs and cats.
The people in the study were asked to text or go online to report their daily symptom scores for runny nose, sneezing, blocked nose, nasal drip and eye symptoms on a scale of zero to three.
The researchers were surprised to find that hayfever symptom scores at the beginning of the season were higher than those at the end of the season for a similar pollen count.
They couldn't explain the difference through medication used, including antihistamines or nasal steroids.
More than half of the people studied were allergic to birch, which comes before the grass pollen season.
However, being allergic to both types of pollen still didn't explain the differences between symptom scores at the beginning and the end of the season.
The research team says it is possible that symptoms appear milder later in the season because people get used to their hayfever, or that the pollen from late flowering species is less allergenic than pollen from early flowering grass.
They also point out that other studies have suggested high exposure to grass pollen early in the season may regulate inflammation later in the year through the production of allergen-fighting T cells.
Dr Letty de Weger from the Department of Pulmonology at Leiden University Medical Centre led the research. Even though she studied people in the Netherlands, she tells us by email that as a near neighbour, the findings are still valid for UK hayfever sufferers: "I would expect a similar pattern of symptoms in the UK. Also in the UK the grass pollen season lasts for several weeks and I think due to this long period the change in symptom severity to a certain grass pollen concentration occurs."
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