Is California Drought Affecting Population IgE Levels?
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
John S. Kaptein, PhD, C.K. E Lin, PhD, Bruce J. Goldberg, MD PhD FAAAAI
Rationale: We noted that the 95thpercentile for some allergen IgE levels varied in different months, and that these varied in annual cycles.  Data indicated that the population’s IgE levels for rye grass pollen were lower in recent years than in prior years.

Methods: Data were obtained for specific IgE testing from a major southern California medical organization.  Rye grass results obtained within a given month were ranked to determine percentiles.  These showed cyclic variation.  Values for 2013-2015 were significantly below a projection based on 2009-2012.  California is experiencing a prolonged years-long drought, so we correlated the population rye grass IgE levels with southern California rainfall data.

Results: Population levels for rye grass IgE were lowest in December-January of each year, rising rapidly to a maximum in May-June and then tapering off.  Rainfall for southern California was less regular but occurs predominantly in October-March.  Population rye grass IgE levels correlated to precipitation occurring four months prior.  This held for seasonal variations and for variations between wet and drought years.  Similar trends were seen with other allergens but not with perennial allergens (e.g. cat dander).

Conclusions: Population levels of rye grass IgE levels were shown to correlate to precipitation occurring four months prior.  During the current California drought the peaks of rye grass IgE were diminished in parallel to the decreased rainfall, with population IgE levels dropping to about 74% of the normal level.  Population IgE levels and likelihood of symptomatic patients may be anticipated based on preceding rainfall levels.