An allergy develops when the immune system mistakenly reacts to harmless substances like pollen, animal dander, dust mites, molds or certain foods. Common symptoms include sneezing, itchy eyes, coughing and difficulty breathing. The document discusses diagnosing allergies through skin prick testing and treating pollen and dust mite allergies with immunotherapy or mite-proof bedding. It also notes that the company offers various allergy-related products to medical facilities.