Allergic disorders occur when the immune system overreacts to substances known as allergens, which can include pollen, dust mites, pet dander, and certain foods. This overreaction can lead to symptoms such as sneezing, itching, hives, and in severe cases, anaphylaxis, a life-threatening reaction that requires immediate medical attention. Common allergic disorders include hay fever, asthma, and eczema. Diagnosis typically involves a medical history review and allergy testing, while treatment options may include avoiding allergens, taking antihistamines, or receiving allergy shots to help desensitize the immune system.