Associate Professor Ian Charlton
GP Asthma Group, National Asthma Council Australia
After 100 years of research into sneezing in spring, is there anything new to report?
Springtime is renowned for the problems it causes hayfever sufferers, but curiously only 20% of patients with allergic rhinitis are troubled during this season.
Most patients have perennial allergic rhinitis, experiencing symptoms on and off throughout the year. This can be attributed to the
wide range of allergens that trigger allergic rhinitis and the fact that plants native to the Australian environment pollinate throughout the year, not just in spring. Nevertheless, the plants that do pollinate in spring tend to be the introduced species and rely on the wind for pollination, producing a much greater pollen load.
Recent studies by researchers in Melbourne have for the first time identified that high grass pollen days, currently defined as more than 50 grains/m3, are days when most sensitive individuals will experience allergic symptoms. However, some asthmatic patients may be at a significant risk even when airborne grass pollen levels are below this level, particularly if there are other airborne triggers such as pollutant particles and gases in the atmosphere.1
Australian researchers were also among the first to recognise ‘thunderstorm asthma’, a potent mix of pollens, weather conditions and rain that can dramatically increase the allergic particles in the atmosphere and trigger severe asthma requiring hospital admission.2
It is now understood that pollen contains nicotinamide adenine dinucleotide phosphate oxidases and bioactive lipid mediators, which may contribute to the inflammatory response.3 These oxidases and mediators are released when rain smashes into the
pollen particles, fracturing them into respirable particles and activating the inflammatory substances.
Controlling rhinitis plays an important role in controlling asthma symptoms, not only because up to 80% of asthma patients have rhinitis as well,4 but also because many of the symptoms attributable to asthma are actually generated by the nose. While the role of ‘postnasal drip’ still arouses great passion, particularly between American and British researchers, it is thought there are possibly five mechanisms by which the performance of the nose can affect the performance of the lungs.
Research data on treating rhinitis to improve asthma is still limited, but this may be due to a lack of studies rather than a lack of evidence. One US study has clearly demonstrated a reduction in emergency department visits and hospitalisation for asthma patients who also had their allergic rhinitis treated.5
So spare a thought for asthma sufferers and their noses. If their noses are not working properly, it is very likely their lungs are also struggling.
For information on asthma diagnosis and management visit the National Asthma Council Australia website at www.nationalasthma.org.au
For information on allergy diagnosis and management visit the Australasian Society of Clinical Immunology and Allergy website at www.allergy.org.au
References
1. Erbas B, Chang JH, Dharmage S, et al. Do levels of airborne grass pollen influence asthma hospital admissions? Clin Exp Allergy 2007;37:1641–7.
2. Bellomo R, Gigliotti P, Treloar A, et al. Two consecutive thunderstorm associated epidemics of asthma in the city of Melbourne. The possible role of rye grass pollen. Med J Aust 1992;156:834–7.
3. Taylor PE, Jacobson KW, House JM, Glovsky MM. Links between pollen, atopy and the asthma epidemic. Int Arch Allergy Immunol 2007;144:162–70.
4. Nayak AS. The asthma and allergic rhinitis link. Allergy Asthma Proc 2003;24:395–402.
5. Crystal-Peters J, Neslusan C, Crown WH, Torres A. Treating allergic rhinitis in patients with comorbid asthma: the risk of asthma-related hospitalizations and emergency department visits. J Allergy Clin Immunol 2002;109:57–62.
Acknowledgement
Wheeze, sneeze and disease
Originally published in GP Review, September 2008. Reproduced with permission.
Download a PDF of this article from the GP Review website: http://www.racgp.org.au/gpreview/200809/27025
Content Updated September 2008
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