What Is Allergies

Allergies occur when the immune system overreacts to typically harmless foreign particles (allergens) in the body. The symptoms that are a result of the immune system’s overreaction range from mild discomfort to life-threatening emergencies depending on the trigger and the allergic person’s individual response.

According the National Institute of Allergy and Infectious Diseases, allergies are widespread in all age groups in the United States. The Centers for Disease Control reports that as of the last census, 2010, allergies are the 6th leading cause of chronic illness in the U.S. with an annual cost in excess of $18 billion. More than 50 million Americans suffer from allergies each year.

The most common types of allergies are:

Food allergies. The list of food allergens as reported by Food Allergy Research and Education Incorporated, a non-profit organization, includes:

  • Peanuts (legume)
  • Tree nuts (walnuts, almonds, hazelnuts, cashews, pistachios, and Brazil nuts)
  • Milk (not to be confused with lactose intolerance, which causes discomfort but is never life-threatening and does not involve an abnormal immune response)
  • Eggs
  • Wheat (not to be confused with gluten intolerance or Celiac disease, which cause discomfort but are never life-threatening and don’t involve abnormal immune responses)
  • Soy
  • Fish
  • Shellfish

The American Academy of Allergy Asthma & Immunology also lists:

  • Strawberries
  • Cherries
  • Grapes

Environmental allergies. Some of these are referred to as seasonal allergies because they are triggered by plant pollen at various times of the year. Others can occur year round. The National Institute of Environmental Health Sciences lists the following as common environmental allergens:

  • Pollen (ragweed, grass, tree)
  • Pets and other animals
  • Mold (also mildew, both caused by a fungi)
  • Dust mites
  • Cockroaches
  • Cigarette smoke

Insect allergies. The American College of Allergy, Asthma & Immunology lists the following stinging insects as potential allergens:

  • Bees
  • Wasps
  • Yellow jackets (a type of wasp)
  • Hornets

Allergies to pets and other animals. Many people are allergic to the dander or saliva of household pets. Cat and dog dander are among the most common pet allergies, though smaller furry animals, such as hamsters, guinea pigs, and other rodents, can also serve as allergens.

Contact allergies. The Asthma and Allergy Foundation of America lists the following substances and materials as potential allergens:

  • Dye for your hair, clothing, leather, furs
  • Nail care products, cosmetics, sunscreen
  • Fragrances, perfumes
  • Rubber compounds, including latex
  • Topical medications
  • Poison ivy, other plants
  • Detergents, cleaning products
  • Metals, especially nickel

Allergies to medications. The American Academy of Allergy Asthma & Immunology lists the following as common medication allergens:

  • Antibiotics, such as penicillin
  • Aspirin and non-steroidal anti-inflammatory medications, such as ibuprofen
  • Anticonvulsants
  • Monoclonal antibody therapy
  • Chemotherapy

What Causes Allergies

Risk Factors For Allergies

Diagnosing Allergies

Symptoms of Allergies


Living With Allergies



Medication And Treatment

Complementary and Alternative Treatment

Care Guide

When To Contact A Doctor

Questions For A Doctor