Allergies
Allergies are an overreaction of the body's immune system to a foreign substance, called an allergen, that is typically harmless. An allergen can be inhaled, ingested, or come into contact with the skin. When the immune system encounters an allergen, it releases chemicals, such as histamine, that cause allergy symptoms.
Here are some of the most common allergens:
- Pollen
- Dust mites
- Mold
- Pet dander
- Food (such as peanuts, milk, eggs, soy, wheat, tree nuts, fish, and shellfish)
- Insect stings
- Medications
Allergy symptoms can vary depending on the allergen and the person. Some common symptoms include:
- Runny or stuffy nose
- Sneezing
- Itchy, watery eyes
- Coughing
- Wheezing
- Skin rash (such as hives or eczema)
- Nausea or vomiting
- Diarrhea