Hay fever symptom severity plateau identified
MedWire News: Study findings suggest that individuals sensitized to Poaceae, a family of land grasses, experience increasing severity in hay fever symptoms in line with daily levels, up to a saturation point.
The study also showed a higher level of nasal and ocular symptoms at the beginning of pollination, which did not have any trigger threshold.
"During natural exposure, decreasing amounts of pollen are required to elicit symptoms as the season progresses, and the severity of allergic response is therefore increased," say Denis Caillaud (Gabriel Montpied Hospital, Cermont-Ferrand, France) and colleagues.
The study included 106 adult patients sensitized to Poaceae (defined as positive skin prick and/or positive immunoglobulin E test) with hay fever symptoms in the past 2 years or longer, living within 30 km of a pollen captor.
Patients were asked to complete a symptom diary during the 4-month Poaceae pollinating period, with the severity of eye, nose, and bronchial symptoms recorded on a 4-point scale from none (0) to severe (3).
Comparison of daily Poaceae with hay fever symptoms showed that the effect of grass pollen on nasal and ocular symptoms was linear, up to a saturation level of 80 and 90 grains/m3, respectively. Above these cutoff points, the effects of the pollens on the symptoms remained constant.
Indeed, for every 10 grain/m3 increase in Poaceae, the risk for experiencing respiratory, nasal, and ocular symptoms significantly increased 1.03, 1.06, and 1.08-fold, respectively, up to the cutoffs of 80-90 grains/m3.
The study also showed that at the start of the season, when pollen levels were below 10 grains/m3, the relationship between ambient pollen levels and nasal or ocular symptoms remained linear but was more pronounced (odds ratio [OR]=2.68 and 1.86, respectively).
Furthermore, individuals with perennial sensitization were at greater risk for nasal symptoms than those without perennial sensitization (OR=4.22 vs 2.37). The authors say this finding may be related to nonspecific pre-priming phenomenon.
Writing in the Journal of Allergy and Clinical Immunology, the researchers conclude: "Our data suggest that pre-priming and priming effects at the beginning of the season without any trigger threshold, a linear response up to a saturation point, then a plateau."
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012
By Ingrid Grasmo