What Are Allergies? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Health ConditionsAllergies

What Are Allergies? Symptoms, Causes, Diagnosis, Treatment, and Prevention

What Are Allergies? Symptoms, Causes, Diagnosis, Treatment, and Prevention
Everyday Health
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Updated on April 15, 2026
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Allergies occur when your immune system overreacts to substances called allergens. Common allergens that can trigger allergic reactions include pollen, pet dander, and bee venom. People also have allergies to certain foods and medications.

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Signs and Symptoms of Allergies

Allergy symptoms vary depending on the type of allergen causing them.

Allergic rhinitis (commonly known as hay fever), for instance, is associated with the following symptoms:

  • Sneezing
  • Runny nose
  • Congestion
  • Itchy eyes, nose, and throat
  • Tearing eyes
An allergic food reaction may share some of the above symptoms, but it can also cause:

  • Diarrhea, nausea, and vomiting
  • Hives, eczema, or itchy skin
  • Anaphylaxis, in which a narrowing of the airways makes it difficult or even impossible to breathe
A skin allergy or insect bite can cause the following at the site:

  • Redness or rash
  • Swelling
  • Hives
  • Pain
  • Itching
The symptoms of a drug allergy may include:

  • Hives or rash
  • Wheezing
  • Lightheadedness
  • Vomiting
  • Swelling of the face or throat, or anaphylaxis

Causes and Risk Factors of Allergies

Your risk of developing allergies is higher if you:

  • Have asthma or eczema
  • Have a family history of asthma or allergies
  • Are younger than 18
Children sometimes outgrow allergies as they get older. It’s also not uncommon for allergies to go away and then return years later.

Children who have food allergies are more likely to also have a respiratory allergy, eczema, or asthma, compared with children who don’t have food allergies.

Allergic Reactions

Allergens are typically harmless substances that trigger an immune response and cause a reaction in people who are allergic. The allergic reaction occurs if the person inhales, touches, swallows, injects, or somehow comes into contact with the allergen. Allergic reactions can be mild, severe, or even life-threatening.

Normally, the immune system protects the body against harmful substances, such as viruses or bacteria. But if you have allergies, “your body responds to allergens as if they were invaders,” explains Clifford Bassett, MD, a clinical assistant professor at New York University Langone Health in New York City. “Your body exaggerates the immune response. That’s what causes histamine release and other things that cause allergy misery.”

The most common allergens that trigger allergic reactions include:

  • Pollen
  • Dust mites
  • Pet dander or fur
  • Mold spores
  • Foods
  • Insect stings or bites
  • Medicines, such as penicillin
  • Latex
Touching certain metals like nickel, cobalt, and chromates can also cause an allergic reaction (contact dermatitis).

Seasonal Allergies

Seasonal allergies and hay fever are usually caused by pollen in the air that appears during different seasons in various places across the country.

Allergy triggers may vary depending on geographic location and climate, but relocating to avoid seasonal allergies generally doesn’t help. Pollen and mold spores travel great distances, and people with allergies often develop sensitivities to other allergens in a different location.

Research shows that environmental factors, such as pollution and climate change associated with rising temperatures, may be contributing to a rise in allergies. Changes in the duration and intensity of pollen and mold seasons mean more people are exposed to allergens for longer amounts of time.

“That’s a longer period of time for your eyes and nose and throat to become symptomatic as a result,” Dr. Bassett says.

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How Are Allergies Diagnosed?

The first step in diagnosing allergies is an evaluation by your physician to review your symptoms and medical history and to rule out other potential medical problems. You can help your doctor make an accurate diagnosis by keeping a record of your symptoms, including when they started and what triggers them.

If allergies are suspected, your doctor may order tests. These include skin and blood tests.

Is It an Allergy or Something Else?

Like allergies, cold and flu affect the respiratory system, and they share some symptoms with allergies. Symptoms like itching, watery eyes, and sneezing, for example, are typical of both a cold and allergies. But if you also have a fever and are only sick for about two weeks, it’s likely a cold or the flu.

One other difference between them is the itchiness associated with many allergic reactions.

“Typically, an allergy will have itchiness of the eyes, nose, and throat,” says Bassett. “With a cold, you’re more likely to have a sore throat, decrease in appetite, and you just don’t feel well.”

Treatment and Medication Options for Allergies

Treatments for allergies are intended to reduce symptoms and improve your quality of life. Allergy treatments vary, depending on the severity of your condition and the type of allergies you have.

Medication Options

If your allergies are severe enough to significantly interfere with your quality of life, or if you aren’t able to find relief using over-the-counter (OTC) treatments, it’s a good idea to see a doctor in order to identify what you’re allergic to and gain access to the full range of prescription options.

OTC medicines include antihistamines and decongestants and nasal steroid sprays (which relieve congestion and previously were only available by prescription). Steroid or antihistamine nasal sprays are now available OTC and may include fluticasone (Flonase) or azelastine (Astelin) and may be used to help prevent or treat allergy symptoms, and there is also montelukast (Singulair), a leukotriene blocker used for asthma and allergic rhinitis.

Your doctor may prescribe allergy shots (immunotherapy), which lessen your immune system’s reaction to allergens. Or, in severe cases, they may prescribe steroids, which reduce inflammation and swelling.

You may also need medications for asthma. If you have severe allergic reactions and are at risk for anaphylaxis, then your doctor may recommend that you carry a dose of epinephrine (Epipen), a chemical that tightens blood vessels and opens airways in the lungs.

Complementary Therapies

Complementary remedies, such as nasal irrigation techniques, may also help relieve allergy symptoms.

A number of other integrative medicine approaches for asthma, eczema, and other allergic symptoms also exist. Options for asthma, for example, include breathing exercises and herbal remedies.

But John Bosso, MD, director of the otorhinolaryngology allergy clinic at Penn Medicine in Philadelphia, cautions people about using these therapies to treat allergies.

“Many things that purport to treat allergies are available because in the supplement/nonpharmaceutical market you don’t need to prove efficacy or that it’s better than placebo — it just needs to be proven to be safe,” he says.

Talk with your doctor to help you determine if some of these therapies may support your treatment goals safely before adding them into your treatment plan.

Disparities and Inequities in Allergies

Of those people who experience allergies and asthma, Black Americans and Hispanics are disproportionately impacted — and they tend to have more serious cases, says Dr. Bosso.

The American Lung Association also notes that people of color are more likely to have air pollution exposure and to experience negative health effects from air pollution, compared with white people, with much of the inequity attributed to the history of systemic racism in the United States.

Lifestyle Changes and Prevention of Allergies

There are some measures you can take to prevent or limit allergic reactions at home, such as:

  • If you’re allergic to pollen, and you know pollen counts are going to be high, try to remain inside with the doors and windows closed.
  • Use a high-efficiency particulate air (HEPA) filter. HEPA filters trap airborne allergens.
  • Wash bedding frequently, and use hot water to lessen your exposure to dust mites.

How Long Do Allergies Last?

Some allergies last for a number of years and then go into remission, and others can last a lifetime, says Bosso.

“For example, a certain percentage of people with asthma and allergic rhinitis can get better with time — often it improves in puberty, especially in boys,” says Bosso.

There are cases in which allergies go away, even if someone has had them a good part of their life.

“A person in their forties or fifties may find that they no longer react to things in the environment,” he says. “Milk and egg allergies are frequently outgrown, but not always. Tree nut allergies are permanent in the majority of people — about 80 percent have it long-term.”

Complications of Allergies

People with allergies are at risk of developing complications that range from mild to potentially life-threatening.

Anaphylaxis

One of the most serious allergic complications is anaphylaxis, which is commonly associated with allergies involving food, drugs like penicillin, and insect venom.

Symptoms of anaphylaxis may include:

  • A drop in blood pressure
  • Loss of consciousness
  • Severe shortness of breath
  • Skin rash
  • Rapid or weak pulse
  • Nausea or vomiting
  • Lightheadedness
  • Severe wheezing
Anaphylaxis is a medical emergency. It can cause seizures, arrhythmia (irregular heartbeat), shock, or respiratory distress.

 If you or someone around you has an anaphylactic reaction, call 911 or seek immediate medical attention.

Asthma

Asthma is a chronic lung disease characterized by inflamed airways and trouble breathing. An asthma attack causes chest tightness, coughing, wheezing, and episodes of severe shortness of breath.

Allergies and asthma are on a spectrum and frequently overlap, Bassett says, adding that the risk of developing asthma if you have allergic rhinitis is significant.

Nasal Polyps

Nasal polyps (growths on the lining of the nose or sinuses) are more commonly seen in people with chronic sinusitis, asthma, or aspirin sensitivity. These growths are noncancerous, but they can obstruct airflow in the nostril.

Other Allergic Complications

People with allergies are also at risk of developing ear or lung infections, as well as sinusitis (sinus infection).

FAQ

What is the definition of allergies?
Allergies are when the immune system recognizes foreign substances called allergens inside the body and attempts to fight them off. Allergens can include pollen, bee venom, and pet dander. Some people may also experience reactions from certain foods and medicines.

Colds and flu affect the respiratory system in the same way that allergies do. But allergies come seasonally every year and stick around, while colds and flu usually only last up to two weeks. A cold or the flu may also come with a fever or body aches, while allergies do not.

Avoiding allergy triggers is the best way to manage allergies. Since some common allergens are hard to avoid, your doctor might recommend certain medications or treatments to reduce the effects of symptoms or lessen the chance of a reaction.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
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  5. Can Relocating Help Allergy Sufferers? American Academy of Allergy Asthma & Immunology. December 11, 2023.
  6. Singh A B et al. Climate Change and Allergic Diseases: An Overview. Frontiers in Allergy. October 13, 2022.
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  10. Nasal Irrigation. Cleveland Clinic. October 12, 2022.
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Jon E. Stahlman, MD

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Jon E. Stahlman, MD, has been a practicing allergist for more than 25 years. He is currently the section chief of allergy and immunology at Children’s Healthcare of Atlanta's Scott...

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Kathleen Hall

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Kathleen Hall is a freelance writer and marketing communications professional. She has a BS in psychology from the University of Maryland and an MBA from Virginia Commonwealth Univ...

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