Thank you for your recent inquiry.
Pollen counts can vary for many different reasons, and changes in wind direction and temperature can result in small differences in the time of maximum concentration. In addition, different pollens may show different variations in the total pollen count according to the time of day or night. In most studies, pollen counts reach a nadir in the early morning hours and then begin to rise sometime after 8:00 a.m., peaking between noon and the late evening hours. This nadir and peak is in part dependent on the individual pollen as well as the location where pollen counts are determined (1, 2).
Thus, in general, it has been found that pollen counts usually demonstrate lower levels in the early morning, and higher levels in the afternoon, but, although the low morning levels usually show consistency between different studies, the peak time can vary considerably from late afternoon until as late as midnight (3). Nonetheless, there are clearcut exceptions to this paradigm depending on location, other climatic conditions, and the particular pollen studied (4, 5).
Thank you again for your inquiry and we hope this response is helpful to you.
Hill JN and Emberlin J. Diurnal variation of pollen concentrations in the air of north-central London. GRANA 1991; 30(1); 229-234.
Pollen count variability. Journal of Allergy and Clinical Immunology 2004; 113(2); Supplement, Page S63.
Spieksma F. Fluctuations in grass pollen counts in relation to nightly inversion and air pollution potential of the atmosphere. International Journal of Biometeorology 1983; 27(2):107-116.
Norris-Haill J. The diurnal variation of Poaceae pollen concentrations in a rural area. GRANA 1999; 38(5); 301-305.
Singh AB. Studies on pollen allergy in Delhi. Diurnal periodicity of common allergenic pollen. Allergy 1980; 35(4):311-317.
Phil Lieberman, M.D.