Allergies

Allergies

Allergies occur when your immune system reacts to a foreign substance such as pollen, bee venom or pet dander that doesn’t cause a reaction in most people.

Symptoms

Allergy symptoms depend on the substance involved and can involve the 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, may cause:

• Sneezing
• Itching of the nose, eyes or roof of the mouth
• Runny, stuffy nose
• Watery, red or swollen eyes (conjunctivitis)

A food allergy may cause:

• Tingling mouth
• Swelling of the lips, tongue, face or throat
• Hives
• Anaphylaxis

An insect sting allergy may cause:

• A large area of swelling (edema) at the sting site
• Itching or hives all over your body
• Cough, chest tightness, wheezing or shortness of breath
• Anaphylaxis

A drug allergy may cause:

• Hives
• Itchy skin
• Rash
• Facial swelling
• Wheezing
• Anaphylaxis

Atopic dermatitis, an allergic skin condition also called eczema, may cause skin to:

• Itch
• Redden
• Flake or peel

Anaphylaxis

Some types of allergies, including allergies to foods and insect stings, have the potential to trigger a severe reaction known as anaphylaxis. A life-threatening medical emergency, this reaction 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

When to see a doctor

You might see a doctor if you have symptoms you think may be caused by an allergy, especially if you notice something that seems to trigger your allergies. If you have symptoms after starting a new medication, call the doctor who prescribed it right away.

Causes

Common allergy triggers include:

• Airborne allergens, such as pollen, animal dander, dust mites and mold
• Certain foods, particularly peanuts, tree nuts, wheat, soy, fish, shellfish, eggs and milk
• Insect stings, such as bee stings or wasp stings
• Medications, particularly penicillin or penicillin-based antibiotics
• Latex or other substances you touch, which can cause allergic skin reactions

Risk factors

You may be at increased risk of developing an allergy if you:

• Have a family history of asthma or allergies.
• Are a child. Children are more likely to develop an allergy than are adults.
• Have asthma or an allergic condition.

Complications

Having an allergy increases your risk of certain other medical problems, including:

• Anaphylaxis is most commonly associated with food allergy, penicillin allergy and allergy to insect venom.
• Asthma an immune system reaction that affects the airways and breathing. In many cases, asthma is triggered by exposure to an allergen in the environment (allergy-induced asthma).
• Atopic dermatitis (eczema), sinusitis, and infections of the ears or lungs.
• Fungal complications such as allergic fungal sinusitis and allergic bronchopulmonary aspergillosis, if you’re allergic to mold.

Tests and diagnosis

To evaluate whether you have an allergy, your doctor may:

• Ask detailed questions about signs and symptoms
• Perform a physical exam
• Have you keep a detailed diary of symptoms and possible triggers

If you have a food allergy, your doctor may:

• Ask you to keep a detailed diary of the foods you eat
• Have you eliminate a food from your diet (elimination diet) — and then have you eat the food in question again to see if it causes a reaction

Your doctor may also recommend one or both of the following tests:

• Skin test
• Blood test

If your doctor suspects your problems are caused by something other than an allergy, you may need other tests to identify — or rule out — other medical problems.

Treatments and drugs

Allergy treatments include:

• Allergen avoidance.
• Medications to reduce symptoms.
• For severe allergies or allergies not completely relieved by other treatment, your doctor may recommend allergen immunotherapy. This treatment involves a series of injections of purified allergen extracts, usually given over a period of a few years.

• Emergency epinephrine.

Prevention

• Avoid known triggers
• Keep a diary
• Wear a medical alert bracelet