Define seasonal allergy and perennial allergy. Give examples of the type of allergens that causes these allergies.

Allergies are one of the common disorders of the human body. An allergy can be defined as an extremely undesirable and potentially harmful response of the body to certain substances that enters our body from the surroundings.

1. Seasonal allergy -The allergies that appear only during certain times of the year . This type of allergy occurs as a result of the exposure to airborne substances. such as pollen grains. Seasonal allergies are commonly called hay fever.
2. Perennial allergy - The allergies that are independent of the seasons and can occur year-round. House dust, mites, pets and animal's feather skin, hair are some allergens that can perennial allergies.

Examples of the type of allergens:

1. Examples of seasonal allergy: Moulds and pollen grains.
2. Examples of perennial allergy: House dust, mites, pets and animal's feather skin, hair .