Many people believe they are allergic to humidity because they develop symptoms on cloudy days, when it rains or when it is foggy. In fact, however, allergy to humidity is allergy to the spores of fungal species in the environment, that develop under these conditions of humidity. The degree of humidity in turn can influence other types of allergy such as that caused by mites or certain types of pollen.

The concentration of spores in the air depends on the meteorological conditions:

• Humidity favours spore growth.
• Sunny weather and winds favour spore release.
• The presence of snow reduces spore growth and release.
• In hot, humid climates, fungi are present throughout the year.
• Air conditioners facilitate the dispersion of spores that have grown in the water accumulated by the de-humidification process.

Principal fungal species:

• Alternaria alternata
• Aspergillus fumigatus
• Cladosporium herbarum
• Penicillium chrysogenum