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Weather and hay fever
For many people, the advent of the warm season is nothing to cheer about. An estimated
10-
Hay fever is a form of allergic rhinitis. But, while allergic rhinitis is an almost constant reaction to a particular substance (allergen), hay fever comes and goes with the seasons: the flowering seasons of trees and grasses, and the sporing season of fungi.
Hay fever has become epidemic with modern times. Every year, medical practitioners of many countries report an increase in consultation numbers. A better awareness amongst the population and/or an increased willingness to consult a professional explains the rising numbers.
Air pollution will aggravate the swelling and irritation of airways. Studies show that pollution increases the sensitivity to allergens. Sufferers of rhinitis become more responsive to allergens when exposed to high doses of ozone, while a link has been established between an increased sensitivity to pollen and vehicle exhaust pollutants, in particular diesel fumes. As a result, the numbers of patients with hay fever are greater in cities than they are in rural areas.
To make matters worse, pollen cells rupture during and after rain and in periods
of lightning. The pollen grains literally explode and release allergen-
Because pollen and spores float easily in the air, updrafts and wind play a vital role in distributing the particles. The first warm days in spring produce vertical air currents, called thermals, that carry the allergens high into the atmosphere. There they catch a ride in the prevailing winds and travel several hundred kilometers before they settle down. Therefore, you can’t necessarily blame your neighbor's flowering ragweed for your stuffy nose.
If the pollen and spores miss the ride, they will settle nearby when the air cools in the evening. Cool and humid air for most of the day will discourage them to travel in the first place. As mentioned earlier, rain can increase the pollen concentration in the short term. But rain is welcomed by hay fever sufferers, nevertheless, as the allergens eventually wash away.