An allergen is a usually harmless substance capable of triggering a response that starts in the immune system and results in an allergic reaction. In addition to pollen, other common allergens include dust mites, animal dander, mold, medications, insect venoms and various foods. Allergens are microscopic and circulate freely via HVAC. (Source: AAAAI)
It is more important to know what person has the disease than which disease the person has
– William Osler
Founding professor of Johns Hopkins Hospital
