Seasonal allergies are reactions which the body produces in response to certain foreign particles, especially pollen. These are different from perennial allergies in terms of the nature of the allergen. Seasonal allergens are mainly pollen from plants and trees which flourish and grow in that particular season. Perennial allergies, as the name suggests are caused due to allergens which are present in the atmosphere all year round, such as allergy from pets, dust, food, and so on.