Allergy Symptoms and Causes
Allergies occur when the immune system overreacts to substances (allergens) that are usually harmless. Allergy types include indoor allergies, pet allergies, dust allergies, mold allergies, animal dander allergies, drug allergies and insect venom allergies.
When a person with allergies breathes in an allergen, the body releases histamine and other chemicals as part of the immune response. This causes itching and swelling, mucus production, and sometimes, hives and rashes. Symptoms vary in severity from person to person.
Symptoms are varied from person to person, and from allergy type to allergy type, but may include:
- Difficulty breathing; wheezing
- Hives; angioedema
- Itchy nose, eyes, throat, or skin
- Red eyes
- Skin rash
- Runny nose
- Sinus pressure
- Tearing eyes
Most environmental allergens contact the skin or eyes, or are inhaled. Therefore, most symptoms affect the skin, eyes, or the breathing passages. Allergic reactions may also develop to indoor or outdoor particles. Common allergy triggers include:
- Animals (dander; saliva)
- Dust (which may contain pollen, mold, fibers from clothing and fabrics, detergents, and microscopic insects such as mites. Dust mites, including small fragments of dead mites, are the primary cause of dust allergy and are found in the highest numbers in bedding, mattresses and box springs).
Some people also develop allergy-like symptoms to other irritants in the environment, including smoke, industrial fumes or cleaning products, tobacco, powders and laundry detergents.