Cloudy days on which the sun remains hidden bring relief from hay fever symptoms. Everyone is familiar with the early morning dew on grasses and plants in the field. To remove this dampness the drying effects of the sun are needed. With the drying of the plants the pollen sacs are opened and the pollens discharged. Any further dampness of the pollens is evaporated by the sun. Under cloudy or humid conditions, the pollens remain dampened and are not spread around in the early morning hours. Thus it is easy to realize how an absence of sunlight brings relief from hay fever symptoms.
Some hay fever sufferers are not benefited by humid conditions or rainy weather. These individuals experience coughing spells and breathing difficulties on damp days or on occasions of sudden thunder storms. Such symptoms may be interpreted as the asthmatic components which accompany pollen hay fever in many cases.
It has long been known that in general, asthmatic persons experience discomfort in damp regions of high humidity. Foggy weather similarly affects asthmatics unfavorably. Dr. Vaughan tells of three epidemics of asthma occurring during unusually heavy fogs. On the other hand some reports have been received in which asthmatic symptoms were increased in environments where the humidity dropped below normal. Three doctors reported attacks of asthma as occurring among a group of pollen sensitive patients on a day in which the weather changed suddenly. All of the patients were in a pollen-free room at the time.
Although these phenomena are not yet completely understood, observations of related barometric pressures have shed some light on the subject. Barometric readings can be used as an indication of atmospheric pressure or humidity. Low barometric readings indicate high humidity. A lowering or falling barometer as it is called, is an indication of rain or an approaching storm.
Cases showing asthmatic symptoms with the commencement of thunder showers are explained on the basis of the fluctuating barometric pressures. It seems that a sudden change in atmospheric pressure, up or down, is accompanied by increased symptoms. A recent experiment with sensitized guinea pigs indicated that during periods of rapid change in meteorological conditions the allergic symptoms were increased by about fifty percent.
Thus we find some hay fever sufferers between the devil and the deep blue sea. Rain keeps the pollen down but brings their asthma out. According to our present state of knowledge relief for the hay feverite who develops asthma is conjectural. The best solution is to take immunizing inoculative treatments which act to prevent the occurrence of asthma.