Allergy
Overview
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
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
When to see a doctor
You might see your health care provider if you have symptoms you think are caused by an allergy, and nonprescription allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the provider who prescribed it right away.
For a severe allergic reaction (anaphylaxis), call 911 or your local emergency number or seek emergency medical help. If you carry an epinephrine auto-injector (Auvi-Q, EpiPen, others), give yourself a shot right away.
Even if your symptoms improve after an epinephrine injection, you should go to the emergency department to make sure symptoms don't return when the effects of the injection wear off.
If you've had a severe allergy attack or any signs and symptoms of anaphylaxis in the past, make an appointment to see your health care provider. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a provider who specializes in allergies and immunology
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.
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 from a bee or wasp
Medications, particularly penicillin or penicillin-based antibiotics
Latex or other substances you touch, which can cause allergic skin reactions
Risk factors
You might be more likely to develop an allergy if you:
Have a family history of asthma or allergies, such as hay fever, hives or eczema
Are a child
Have asthma or another allergic condition
Complications
Having an allergy increases your risk of certain other medical problems, including:
Anaphylaxis. If you have severe allergies, you're at increased risk of this serious allergy-induced reaction. Foods, medications and insect stings are the most common triggers of anaphylaxis.
Asthma. If you have an allergy, you're more likely to have 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).
Sinusitis and infections of the ears or lungs. Your risk of getting these conditions is higher if you have hay fever or asthma.
Prevention
Preventing allergic reactions depends on the type of allergy you have. General measures include the following:
Avoid known triggers.
Keep a diary.
Wear a medical alert bracelet.