$A$ person shows strong unusual hypersensitive reactions when exposed to certain substances present in the air. Identify the condition. Name the cells responsible for such reactions. What precaution should be taken to avoid such reactions?

(N/A) The condition is known as Allergy. It is the hypersensitive response of the immune system to certain antigens present in the environment.
Mast cells are responsible for such reactions as they release chemicals like histamine and serotonin.
To avoid such reactions,the following precautions should be taken:
$(i)$ The use of drugs like antihistamines,adrenaline,and steroids can quickly reduce the symptoms of allergy.
$(ii)$ Identify and avoid contact with the specific allergens (substances) to which the person is hypersensitive.