How allergies develop

Allergens develop in two phases.

Phase 1

First, your immune system responds to certain substances by creating antibodies called immunoglobulin E (IgE). This part is called sensitization.

Depending on what kind of allergy you have, such as pollen or food, these antibodies are localized in your airways — including your nose, mouth, throat, windpipe, and lungs — your gastrointestinal (GI) tract, and your skin.

Phase 2

If you’re exposed to that allergen again, your body releases inflammatory substances, including the chemical histamine. This causes blood vessels to dilate, mucus to form, skin to itch, and airway tissues to swell up.

This allergic reaction is meant to stop allergens from getting in and to fight off any irritation or infection that might be caused by the allergens that do get in. Essentially, you can think of allergies as an overreaction to those allergens.

From then on, your body responds similarly when it’s exposed to that allergen in the future. For mild airborne allergies, you might experience symptoms of puffy eyes, stuffy nose, and itchy throat. And for severe allergies, you might have hives, diarrhea, and trouble breathing.

When allergies typically develop

Most people remember first getting allergy symptoms at a young age — about 1 in 5 kids have some kind of allergy or asthma.

Many people outgrow their allergies by their 20s and 30s, as they become tolerant to their allergens, especially food allergens such as milk, eggs, and grains.

But it’s possible to develop an allergy at any point in your life. You may even become allergic to something that you had no allergy to before.

It isn’t clear why some allergies develop in adulthood, especially by one’s 20s or 30s.

Let’s get into how and why you can develop an allergy later in life, how you can treat a new allergy, and whether you can expect a new allergy or an existing one to go away with time.

Common adult allergies

Seasonal allergies

The most commonly developed adult-onset allergies are seasonal. Pollen, ragweed, and other plant allergens spike at certain times of the year, usually the spring or fall.

Pet allergies

Have a feline or canine friend? Being constantly exposed to their dander, or skin flakes that slough off and become airborne, and chemicals from urine and saliva that get on dander can cause you to develop an allergy.

Food allergies

Nearly 11 percent of adults in the United States have some type of food allergy, and nearly half of them report first noticing symptoms during adulthood, especially to certain kinds of fish.

Other common food allergens in adults are peanuts and tree nuts and fruit and vegetable pollen.

Many children develop food allergies and often have less and less severe symptoms as they get older.

Why does this happen?

It isn’t exactly clear why allergies might develop in adulthood.

Researchers believe that a severe allergic reaction during childhood, even a single episode of symptoms, can increase your likelihood of developing allergies as an adult when you’re re-exposed to that allergen at higher levels.

In some cases, these links are easy to see and represent what is known as the atopic march. Children who have food allergies or skin conditions like eczema may develop symptoms of seasonal allergies, like sneezing, itching, and sore throats, as they get older.

Then, symptoms fade for a while. They may return in your 20s, 30s, and 40s when you’re exposed to an allergy trigger. Possible adult allergy triggers can include:

  • Allergen exposure when your immune system function is reduced. This happens when you’re sick, pregnant, or have a condition that compromises your immune system.
  • Having little exposure to an allergen as a child. You may not have been exposed to high enough levels to trigger a reaction until adulthood.
  • Relocating to a new home or workplace with new allergens. This could include plants and trees that you weren’t exposed to before.
  • Having a pet for the first time. Research suggests this can also happen after a long period of having no pets.

Can allergies go away with time?

The short answer is yes.

Even if you develop allergies as an adult, you may notice they start to fade again when you reach your 50s and beyond.

This is because your immune function is reduced as you get older, so the immune response to allergens also becomes less severe.

Some allergies you have as a child may also go away when you’re a teen and well into your adulthood, perhaps making only a few appearances throughout your life until they disappear permanently.


Here are some possible treatments for allergies, whether you have a mild seasonal allergy or a severe food or contact allergy:

  • Take antihistamines. Antihistamines, such as cetirizine (Zyrtec) or diphenhydramine (Benadryl), can reduce your symptoms or keep them under control. Take them before you’re exposed to an allergen.
  • Get a skin-prick test. This test can help you see what specific allergens trigger your reactions. Once you know what you’re allergic to, you can try to avoid that allergen or reduce your exposure as much as possible.
  • Consider getting allergy shots (immunotherapy). The shots can gradually build up your immunity to your allergy triggers within a few years of regular shots.
  • Keep an epinephrine auto-injector (EpiPen) nearby. Having an EpiPen is important in case you’re accidentally exposed to an allergy trigger, which can result in low blood pressure and throat swelling/airway constriction that makes it hard or impossible to breathe (anaphylaxis).
  • Tell the people around you about your allergies. If your symptoms can be severe or life threatening, they’ll know how to treat you if you have an allergic reaction.

When to see a doctor

Some allergy symptoms are mild and can be treated with reduced exposure to the allergen or by taking medication.

But some symptoms are severe enough to disrupt your life, or even life threatening.

Seek emergency medical help, or have someone around you get help if you notice any of the following symptoms:

  • feeling abnormally dizzy
  • abnormal swelling of the tongue or throat
  • rash or hives across your body
  • abdominal cramps
  • throwing up
  • diarrhea
  • feeling confused or disoriented
  • fever
  • anaphylaxis (throat swelling up and closing, wheezing, low blood pressure)
  • seizures
  • loss of consciousness

The bottom line

You can develop allergies at any time during your life.

Some may be mild and depend on seasonal variations in how much of that allergen is in the air. Others may be severe or life threatening.

See your doctor if you start to notice new allergy symptoms so that you can learn what treatment options, medications, or lifestyle changes may help reduce your symptoms or keep them under control.