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Autum brings rainfall but that can be harmful for allergic patients. In the summer time symptoms were rare but whe its over, respiratory patients start again to notice the symtoms.
The cause is the rise in relative humidity, making it easier to grow for mites.
Whenever humidity falls down, the life span of the mite gets longer. The champion in this game of survival in dry conditions is dermatophagoides farinae, able to stand a few dry months and take advantge of short humid periods of time to finish its growing cycle.
Patients sentitive to dust mites worsen in damp areas and when the rainfall comes. Classic studies show the rise in mite concentration close to Ducth canals (humid) and a dramatically decrease in (drier) inner areas.
An ideal measure would be keeping relative humidity lover than 50%, but that is no easy task because house activities (cooking, cleaning) do rise humidity. Nonetheles it has been seen up to 90% decrease in mite population keeping relative humidity below 35% during 16 hours.
The bedroom is one of the highest growing mite areas of the house. In matresses the dampness is lower but temperature is higher when beds are occupied. Human body gives a rise in humidity (even higher due to perspiration) that may be enough for mites to complete their life cycle. Just breathing on pillows or matresses may be enough for mites to grow.
Enviromental measures are still being recommended as a non-allways effective accesory treatment instrument. Symptom control with the new antiallergic drugs and the reeducation of the immune system with allergy shots may bring back to normality to the patient.