Im happy i dont have allergies
Yes, they cause many issues to the immune system.
oh yea i bet, really gets bad
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 diseases include hay fever, food allergies, atopic dermatitis, allergic asthma, and anaphylaxis. Symptoms may include red eyes, an itchy rash, sneezing, a runny nose, shortness of breath, or swelling. Food intolerances and food poisoning are separate conditions.
Common allergens include pollen and certain food. Metals and other substances may also cause problems. Food,
Bet v I allergen
Bet v I allergen is a family of protein allergens. Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms. 
Trees within the order Fagales possess particularly potent allergens, e.g. the prototypical Bet v 1, the major white birch ("Betula verrucosa") pollen antigen. Bet v 1 is the main cause of type I allergies observed in early spring. Type