An allergy is an abnormal and exaggerated immune system response to a substance that is typically harmless to most people. This substance, known as an allergen, triggers an immune reaction in individuals who are allergic to it. Common allergens include pollen, dust mites, certain foods (e.g., peanuts, shellfish, dairy), insect stings, pet dander, and certain medications.
When a person with allergies comes into contact with an allergen, their immune system produces antibodies called immunoglobulin E (IgE). These antibodies bind to mast cells and basophils, which are types of immune cells in the body.
Upon subsequent exposure to the same allergen, the allergen binds to the IgE antibodies on mast cells and basophils, triggering the release of chemicals such as histamine. Histamine and other chemicals cause various allergic symptoms, which can range from mild to severe. Common allergy symptoms include:
- Sneezing
- Runny or stuffy nose
- Itchy or watery eyes
- Skin rashes or hives
- Swelling (angioedema)
- Coughing and wheezing
- Gastrointestinal symptoms (e.g., nausea, diarrhea) in the case of food allergies
- Anaphylaxis, a severe and potentially life-threatening reaction characterized by difficulty breathing, drop in blood pressure, and swelling of the throat and tongue
Allergies can affect various parts of the body and can be triggered by a wide range of allergens. Allergic reactions can vary in severity, with some individuals experiencing mild symptoms, while others may have severe and even life-threatening reactions.
Diagnosis of allergies typically involves a combination of medical history, physical examination, and allergy testing. Allergy testing can include skin prick tests, blood tests for specific IgE antibodies, and oral food challenges, among others.
Management of allergies often involves allergen avoidance, medication to alleviate symptoms (e.g., antihistamines, decongestants), and, in some cases, allergen immunotherapy (allergy shots) to desensitize the immune system. For severe allergies, individuals may carry epinephrine auto-injectors to treat anaphylactic reactions.
Understanding and managing allergies are essential to improving the quality of life for individuals affected by them and ensuring that allergic reactions are treated promptly and effectively.