Allergies

Allergies

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.

An allergy starts when your immune system mistakes a normally harmless substance for a dangerous invader. The immune system then produces antibodies that remain on the alert for that particular allergen. When you're exposed to the allergen again, these antibodies can release a number of immune system chemicals, such as histamine, that cause 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

Anaphylaxis

Some types of allergies, including allergies to foods and insect stings, can trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, anaphylaxis can cause you to go into shock. Signs and symptoms of anaphylaxis include:

• Loss of consciousness

• A drop in blood pressure

• Severe shortness of breath

• Skin rash

• Lightheadedness

• A rapid, weak pulse

• Nausea and vomiting

Prevention

Preventing allergic reactions depends on the type of allergy you have. General measures include the following:

• Avoid known triggers. Even if you're treating your allergy symptoms, try to avoid triggers. If, for instance, you're allergic to pollen, stay inside with windows and doors closed when pollen is high. If you're allergic to dust mites, dust and vacuum and wash bedding often.

• Keep a diary. When trying to identify what causes or worsens your allergic symptoms, track your activities and what you eat, when symptoms occur and what seems to help. This may help you and your provider identify triggers.

• Wear a medical alert bracelet. If you've had a severe allergic reaction, a medical alert bracelet (or necklace) lets others know that you have a serious allergy in case you have a reaction and you're unable to communicate.