Question

Define
1 allergy
2 allergen
With example

Answer 1

1) Allergy

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment.
These include:

Drug Allergy
An abnormal reaction of the immune system to a medication.
Food allergies
An unpleasant or dangerous immune system reaction after a certain food is eaten.
Animal allergy
An abnormal immune reaction to proteins in an animal's skin cells, saliva or urine.

2) Allergens
Those substances which causes allergic diseases are known as allergens
These are found in dust mites, pets, pollen, insects, ticks, moulds, foods and some medicines

Common allergens are animals, plant pollens, metal, latex, wood, dust, etc