It's what happens when your immune system reacts to something that’s usually harmless. Those triggers, which doctors call "allergens," can include pollen, mold, and animal
dander, certain foods, or things that irritate your skin. Allergies are very common. At least 1 in 5 Americans has one. It starts when you come into contact with a trigger that you inhale,
swallow, or get on your skin. In response, your body starts to make a protein called IgE, which grabs onto the allergen. Then histamine and other chemicals get released into the blood. That
causes the symptoms you notice. Your symptoms depend on how you’re exposed -- through the air, your skin, food, or through an insect sting. If you’ve got a nasal allergy (one that's triggered by something you inhale), common symptoms include: Common symptoms of a skin allergy include rashes
and hives (a rash with raised red patches). Your skin may be red, itchy, or swollen. Food allergies can also
cause stomach cramps, vomiting, and diarrhea. If an
insect sting was the trigger, you’ll have swelling, redness, and pain where it stung you. Symptoms can range from mild to severe. Most go away shortly after the exposure stops. Mild ones may be almost unnoticeable. You might just feel a little “off.” Moderate symptoms can make you feel ill, as if you’ve got a cold or even the
flu. Severe allergic reactions are extreme. The most severe allergic reaction is called anaphylaxis. It affects your whole body. Symptoms can include: Tingling in the hands, feet, lips, or scalp Anaphylaxis is life-threatening, so call 911 right away. If you have an
epinephrine auto-injector, use it and repeat after 5 to 15 minutes if your symptoms haven’t improved. You’ll still need medical care right after you give yourself the shots, even if your symptoms seem to stop, because a delayed reaction could still happen. OverviewAllergies 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. SymptomsAllergy 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:
AnaphylaxisSome 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:
When to see a doctorYou 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. Sign up for free, and stay up to date on research advancements, health tips and current health topics, like COVID-19, plus expertise on
managing health. To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that
information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail. CausesAn 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:
Risk factorsYou might be more likely to develop an allergy if you:
ComplicationsHaving an allergy increases your risk of certain other medical problems, including:
PreventionPreventing allergic reactions depends on the type of allergy you have. General measures include the following:
Aug. 05, 2022 |