One in five US homes are affected by asthma and allergies
Some allergens are just 0.5 microns in size – approximately 200 times smaller in diameter than a human hair. Many start life in the home, like dust mites and their faeces. Others, such as pollen, enter through open windows. When allergy sufferers inhale allergens or come into contact with them, their immune systems overreact, producing antibodies to repel them. Sneezing, coughing or a runny nose – an allergic reaction.