"-Some people, when they come into contact with airborne,animals and  plants, will experience allergic reactions. 
-Why do these reactions happen? 
When a person is exposed to allergens produced by animals or plants, their body produces antihistamine or histamine compounds through the activation of antigen-antibody reactions. This results in allergic symptoms such as fever, asthma, and dermatitis.
-nowadays specific tests are used to trigger allergic reactions for diagnostic purposes