Seasonal allergic rhinitis, more commonly known as hay fever, seems to be arriving earlier each year. Contrary to some media reports, however, this is one phenomenon we cannot blame on global warming. According to Dr Paul Dowding, senior lecturer in botany and environmental science at Trinity College Dublin, we should point the finger at high-speed rotary mowers and strimmers instead.
I first met Dowding during my undergraduate years in Trinity. He taught an interesting module to medical students - "Man and his Environment" - which succeeded in getting many future doctors to think beyond a narrow disease model for the first time. Dowding is also the man to thank for the accurate measurement of pollen levels in the Dublin area. He started the Pollen Counting Service in 1976 and by 1980 he had developed an accurate pollen forecasting model which is still in use both here and in the UK.
So when he says, in the latest Asthma Society newsletter, that the draughts created by modern mowers are sufficient to get grains of pollen airborne and into human airways, I think we should listen. He has also identified a weed grass called "Poa Annua" which flowers as early as February. Although low-growing in comparison to other grasses, the strimmers and rotary mowers are capable of launching microdroplets of Poa into the path of early season gardeners.
Allergy sufferers would be well advised to wear eye, nose and throat protection while mowing to avoid an early season dose of hayfever. Above-average temperatures in March, April and May can also bring forward the start of the grass pollen season.
Despite the rhinitis label, hayfever affects eyes, throat and chest as well as the nasal passages. Some people will notice itchy eyes more than a runny nose, while for others uncontrollable sneezing or even bouts of wheezing are the principal complaints.
These are brought about by an over-reaction of the body's immune system to the presence of pollen in the lining of the throat, nose and eyes. The resulting inflammatory response ensures hours of misery for the unfortunate sufferer, a response which lasts long after pollen exposure has ceased.
Kieran O'Driscoll, an ear, nose and throat specialist at Tullamore General Hospital, has just published the first Irish analysis of allergic rhinitis. The study, carried out with the assistance of the GP Training Unit at Tullamore, was based on identical research which looked at the prevalence of the disease in an urban population in Nottingham in 1998.
O'Driscoll found a prevalence of hay fever of 16 per cent, which is slightly lower than that found in the UK survey. His research targeted a population of 205,000 people in the counties of Offaly, Laois, Longford and Westmeath. The most interesting finding, however, was the high prevalence of sinusitis in the rural Irish population compared with the urban-based UK study. "This may well reflect the prolonged seasonal element of nasal symptoms in the rural environment of the midlands," according to O'Driscoll. The diversity of pollen and spores has been well documented in botanical studies of boglands.
So this piece of research ties in with the findings of Dr Paul Dowding: a prolonged "hay fever" season will result in chronic rhinitis and sinusitis. And it certainly makes sense to doctors who are seeing more patients with inflamed and fluid-filled sinuses - often a difficult condition to treat effectively.
The standard treatment for hay fever is a combination of antihistamines, topical steroid drops and sprays, and mast cell stabilisers, which act directly on the immune system to prevent it from going into overdrive. Some people with severe symptoms require a seasonal injection of steroids.
What else can you do to minimise the problem? Try to avoid contact with allergens by staying indoors when pollen counts are high. Keep windows closed when sleeping. Vacuum your home and dampen down dust regularly. Air duvets and blankets in direct sunlight. And be sure to wear eye, nose and mouth protection when tackling your garden with modern appliances.
The TCD Botany Department website is a good source of information on pollen forecasting and has useful hints for hay fever sufferers: www.tcd.ie/botany
Contact Dr Houston at mhouston@irish-times.ie or leave messages at 01-6707711 ext 8511