Allergies occur when your immune system reacts to a foreign substance â such as pollen, bee venom or pet dander â 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 â a potentially life-threatening emergency. While most allergies can't be cured, treatments can help relieve your allergy 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:
A food allergy can cause:
An insect sting allergy can cause:
A drug allergy can cause:
Atopic dermatitis, an allergic skin condition also called eczema, can cause skin to:
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:
You might see a doctor if you have symptoms you think are caused by an allergy, and over-the-counter allergy medications don't provide enough relief. If you have symptoms after starting a new medication, call the doctor 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 doctor. Evaluation, diagnosis and long-term management of anaphylaxis are complicated, so you'll probably need to see a doctor 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:
To evaluate whether you have an allergy, your doctor will likely:
If you have a food allergy, your doctor will likely:
Your doctor might also recommend one or both of the following tests. However, be aware that these allergy tests can be falsely positive or falsely negative.
If your doctor suspects your problems are caused by something other than an allergy, other tests might help identify â or rule out â other medical problems.
Having an allergy increases your risk of certain other medical problems, including:
Preventing allergic reactions depends on the type of allergy you have. General measures include the following:
Clinical practice guidelines suggest that some people with allergic rhinitis may benefit from acupuncture.
Some allergy symptoms improve with home treatment.
You might be more likely to develop an allergy if you: