Allergies: Basic Info You Need to Know

Medically Reviewed by Jabeen Begum, MD on September 20, 2023
3 min read

You get allergies when your immune system responds to substances such as pollen, pet dander, or certain foods. Your antibodies identify these allergens as bad for you, even though they're not.

Allergies are very common. At least 1 in 3 American adults and 1 in 4 children have them.


Allergic reactions happen when you come into contact with an allergen. Your immune system reacts by releasing histamines and other chemicals into your blood, causing symptoms that can irritate your skin, sinuses, or digestive system.

Common allergens include:

  • Airborne allergens: pollen, pet dander, dust mites, mold
  • Certain foods: peanuts, tree nuts, shellfish, eggs, and dairy
  • Insect stings: bees and wasps
  • Medications
  • Latex

Your allergy symptoms will vary depending on what you're allergic to and how you’re exposed. Allergens can enter your body in several ways:

  • Through your nasal passages and into your lungs
  • Through your mouth
  • Through your skin
  • Through absorption from an insect sting

If you have a mild allergic reaction, common symptoms might be:

Symptoms of a food allergy could include:

An allergic reaction to an insect sting might cause any of these:

  • Swelling, redness, and pain at the site of the sting
  • Itching or hives
  • Chest discomfort or tightness
  • Cough
  • Anaphylaxis

A severe allergic reaction could produce problems such as:

  • Abdominal pain
  • Anxiety
  • Chest tightness
  • Cough
  • Diarrhea
  • Difficulty breathing or swallowing
  • Dizziness
  • Swelling of the face, eyes, or tongue
  • Anaphylaxis

If you have any of these severe symptoms, call your doctor or seek medical attention immediately.

Some allergic reactions are mild, but others can produce life-threatening problems, including anaphylaxis, which is a whole-body allergic reaction. You have to treat anaphylaxis with epinephrine (adrenaline) within minutes.

If you have an epinephrine auto-injector, use it and repeat after 5 to 15 minutes if your symptoms haven’t improved. You still need to get medical care after using an EpiPen, even if you get better.

Signs of anaphylaxis include:

  • Hives and itching all over
  • Wheezing or shortness of breath
  • Hoarseness or tightness in your throat
  • Swelling of your face, eyelids, lips, tongue, or throat
  • Tingling in your hands, feet, lips, or scalp

If you have any signs of anaphylaxis, call 911.

There is no cure for allergies, including what you eat. But your diet might help with how bad your symptoms get. Here are some of the foods that researchers are studying to see if they might help or make allergies worse.

Good fats
Researchers are studying whether polyunsaturated fatty acids such as omega-3s can help prevent allergies in children. Foods such as salmon, mackerel, tuna, flaxseeds, chia seeds, and walnuts are high in omega-3s, which help ease inflammation. Researchers think eating these may lower the risk of childhood asthma and allergy.

In one Swedish study, children who had higher levels of these fatty acids in their blood at age 8 were less likely to have nasal allergies by age 16. However, more research is needed to confirm if that is because of the polyunsaturated fatty acids in their diets or something else.

Mediterranean diet
A large study of children in Crete (part of Greece) found that children who stuck to a Mediterranean diet full of fruits, vegetables, whole-grain breads and cereals, and legumes and nuts were less likely to have hay fever.

Show Sources


American Academy of Allergy Asthma and Immunology.

Asthma and Allergy Foundation of America: “What Is an Allergy?” “Immunoglobulin E (IgE) Defined.”

Journal of Allergy & Clinical Immunology: “Polyunsaturated fatty acids in plasma at 8 years and subsequent allergic disease.”

Mayo Clinic: “Allergies Overview.”

MedlinePlus: “Allergic Reactions.”

National Institutes of Health: “Omega-3 Fatty Acids.”

Thorax: “Protective effect of fruits, vegetables and the Mediterranean diet on asthma and allergies among children in Crete.”

William Larry Haith, DO, FAAEM, Consulting Staff, Department of Emergency Medicine, Southern Maine Medical Center.

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