Allergies occur when your immune system reacts to a foreign substance — such as pollen, bee venom or pet dander — or a food that doesn’t cause a reaction in most people.
Your immune system produces substances known as antibodies. When you have allergies, your immune system makes antibodies that identify a particular allergen as harmful, even though it isn’t. When you come into contact with the allergen, your immune system’s reaction can inflame your skin, sinuses, airways or digestive system.
The severity of allergies varies from person to person and can range from minor irritation to anaphylaxis — a potentially life-threatening emergency. While most allergies can’t be cured, treatments can help relieve your allergy symptoms.
Symptoms
Allergy symptoms, which depend on the substance involved, can affect your airways, sinuses and nasal passages, skin, and digestive system. Allergic reactions can range from mild to severe. In some severe cases, allergies can trigger a life-threatening reaction known as anaphylaxis.
Hay fever, also called allergic rhinitis, can cause:
Sneezing
Itching of the nose, eyes or roof of the mouth
Runny, stuffy nose
Watery, red or swollen eyes (conjunctivitis)
A food allergy can cause:
Tingling in the mouth
Swelling of the lips, tongue, face or throat
Hives
Anaphylaxis
An insect sting allergy can cause:
A large area of swelling (edema) at the sting site
Itching or hives all over the body
Cough, chest tightness, wheezing or shortness of breath
Anaphylaxis
A drug allergy can cause:
Hives
Itchy skin
Rash
Facial swelling
Wheezing
Anaphylaxis
Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:
Itch
Redden
Flake or peel
