The Basics of Allergies

Reviewed by: HU Medical Review Board | Last reviewed: March 2022

Allergies are some of the most common chronic (long-term) health conditions in the world. About 50 million people in the United States have some form of allergy. Allergies affect people of all ages, races, income levels, and genders.1,2

People can be allergic to just about anything. The most common allergies are to:1

  • Foods
  • Insects
  • Animals
  • Things in the environment, such as pollen, mold, dust, or chemicals
  • Latex
  • Medicines

What is an allergy?

Someone is said to have an allergy if their immune system overreacts when it comes in contact with an allergen. An allergen is anything that triggers an allergic reaction. The most common allergens are:1

  • Pollen
  • Dust
  • Food
  • Insects
  • Animals
  • Mold
  • Certain drugs
  • Latex

People often confuse an intolerance for an allergy. With an allergy, the immune system responds when coming into contact with an allergen. With an allergy, even a tiny amount can trigger a full allergic reaction or even anaphylaxis. Anaphylaxis is a life-threatening allergic reaction.3

With an intolerance, the immune system does not react. Another system, such as the gastrointestinal system, responds to a substance. Intolerances are not life-threatening. An example would be lactose intolerance versus a milk allergy.3

What causes an allergic reaction?

A healthy immune system helps protect your body from bacteria, viruses, fungi, or cancer cells. The immune system responds to these “invaders” by attacking them.

If you have an allergy, your immune system reacts to a common thing like it is a danger even though it is not. When you come into contact with that substance, your immune system causes symptoms. Symptoms may range from itchy skin to shortness of breath to stomach upset.2

What are the symptoms of allergies?

Symptoms of allergies can range from mild to severe. The severity of symptoms depends on the person, how much they were exposed, and what they are allergic to. Some symptoms may even be life-threatening.

Mild to moderate allergy symptoms may include:2,3

  • Sneezing, runny, or stuffy nose
  • Watery, red, or swollen eyes
  • Tingling in the mouth
  • Swelling of lips, tongue, throat, or face
  • Cough, chest tightness, or wheezing
  • Hives, itching, rash, reddening of the skin
  • Swelling at the site of an insect sting or where a chemical touched you
  • Stomach pain or upset
  • Diarrhea, nausea, or vomiting

The most severe allergic reaction is anaphylaxis. It is life-threatening. Signs of anaphylaxis include:2

  • Drop in blood pressure
  • Lightheadedness
  • Weak, rapid pulse
  • Nausea and vomiting
  • Loss of consciousness
  • Shortness of breath

Anaphylaxis is so dangerous because symptoms come on quickly and involve 2 or more organ systems.2

If you have symptoms of anaphylaxis and you carry epinephrine, give yourself an epinephrine injection right away. Then, call 9-1-1 or go to an emergency room as quickly as possible.

How are allergies diagnosed?

Allergies may be diagnosed by a pediatrician, family doctor, or a specialist called an allergist. An allergist is an immunologist with extra training in diagnosing and treating allergies and asthma. Depending on the type of allergy you think you have, your doctor may diagnose you with these tools:1,3

  • Physical exam
  • Symptom diary
  • Blood tests
  • Skin test
  • Lung function test
  • Other tests to rule out other conditions

Having a diagnosis is important to help guide treatment. It will also help you avoid the things that trigger your allergies.

How are allergies treated?

The first step in treating an allergy is to understand what you are allergic to. That is because treatments depend on the type of allergy you have and your symptoms. It is also important to learn the difference between normal symptoms and those that are life-threatening.

The most common treatments include:4

  • Avoiding allergens or reducing your exposure
  • Over-the-counter drugs
  • Prescription drugs
  • Immunotherapy
  • Emergency epinephrine auto-injector (EpiPen®, Adrenaclick®, Auvi-Q®, Symjepi®)

It is also important to educate those closest to you about your allergy and how to respond in an emergency.

The goals of allergy treatment include the ability to:

  • Work or go to school comfortably
  • Sleep well
  • Enjoy normal activities
  • Manage reactions if they do occur

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