Environmental Allergies

Environmental allergies cause your immune system to react to normally harmless substances. Common causes include pollen, dust, mold and pet dander. Symptoms include congestion, itchy nose, fatigue, headache, watery eyes and sneezing. Treatment includes antihistamine medications and avoiding known allergens.


What are environmental allergies?

Environmental allergies are substances in your environment that cause your immune system to overreact. Usually, these substances — called allergens — are harmless. But if you have an allergy to a particular substance in your environment, your immune system overreacts to its presence in your body.

Who do environmental allergies affect?

Environmental allergies can affect anyone.

You’re more likely to have or develop environmental allergies if your biological parents have environmental allergies.

How common are environmental allergies?

Environmental allergies are very common. Approximately 24 million people in the U.S. have environmental allergies.


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How do environmental allergies affect my body?

Environmental allergies cause an allergic reaction. An allergic reaction is your body’s response to an allergen. You can be sensitive to one or more allergens.

If you have allergies, the first time you encounter an environmental allergen, your body responds by creating immunoglobulin E (IgE). IgE are antibodies your immune system makes, which target specific kinds of allergens. IgE antibodies bind to mast cells (histamine-containing cells) in your mucus membranes, skin, gastrointestinal (GI) tract and airways. After your first exposure, the IgE-armed mast cells are now sensitive to the specific allergens. The next time you encounter the allergens, the IgE binds to the allergen, triggering the mast cells to release histamine and other chemicals.

Histamine is what causes your immediate allergy symptoms. Your symptoms develop very fast — usually within seconds or minutes. The other chemicals can cause ongoing inflammation.

You can also have a non-IgE reaction to certain irritants. Your body reacts to volatile organic compounds (VOCs), which are gases that enter the air from products or processes. Non-IgE reactions are similar to IgE reactions and involve your immune system, but not IgE antibodies. Examples of common environmental irritants that cause non-IgE reactions include dust, smoke, paint fumes and perfumes or colognes.

Symptoms and Causes

What are the symptoms of environmental allergies?

Environmental allergy symptoms include:

Seasonal allergies can also trigger an asthma attack.


What causes environmental allergies?

Environmental allergens include many different substances, including:

  • Pollen. Pollens are microspores from trees, grass or weeds that appear as a fine dust. Pollen may be many colors, including yellow, white, red or brown. Plants release pollen to fertilize other plants for reproduction. Pollen levels are usually highest in the morning. Pollen levels increase on warm, windy days.
  • Molds. Molds are tiny fungi (singular, fungus). They have spores that float in the air. Mold is common in damp areas with little or no airflow. These areas may include your basement, kitchen or bathroom. Mold also grows outdoors in leaf piles, grass, mulch, hay or under mushrooms. Mold spore levels are highest during hot, humid weather.
  • Pet dander and saliva (spit). Pet dander is tiny scales from your pet’s skin, hair or feathers. Your pet’s sweat glands secrete proteins through their skin, which collect in their skin and fur and may cause an allergic reaction. Your pet’s spit (saliva) also contains these proteins.
  • Dust mites. Dust mites are tiny, eight-legged relatives of spiders. They’re too small to see with your eyes. They live on bedding, mattresses, carpets, curtains and upholstered (fabric) furniture. They feed on the dead skin cells that you and your pets shed. Dust mites live on every continent except Antarctica, but they thrive in hot, humid environments. They don’t bite you. Breathing in the proteins from their urine (pee), feces (poop) and dead bodies may cause allergic reactions.
  • Cockroaches. Cockroaches are reddish-brown or black insects that are 1.5 to 2 inches long. Male cockroaches have two pairs of wings. Many female cockroaches don’t have wings. If they have wings, they aren’t strong enough to allow flight (vestigial wings). The proteins in their poop, spit, eggs and dead body parts may cause allergic reactions.

Examples of environmental irritants that cause non-IgE reactions include:

  • Smoke. Smoke of any kind can trigger a non-IgE reaction. The chemicals in these products can cause irritation that’s similar to an allergic reaction. Examples include tobacco product smoke — including cigarettes, vapes and cigars — and marijuana and scented candle smoke.
  • Dust. Dust is a combination of tiny particles of matter. Dust may include dead skin cells, hair, pollen, clothing fibers, dust mites, dead insect pieces, dirt, bacteria and tiny pieces of plastic.

Are environmental allergies contagious?

No, environmental allergies aren’t contagious. You can’t spread your environmental allergies to another person.

Diagnosis and Tests

How are environmental allergies diagnosed?

An allergist is a healthcare provider who specializes in allergies. They can help you diagnose your environmental allergies through tests.

Before conducting environmental allergy tests, they may ask you questions, including:

  • Do you have a family history of environmental allergies?
  • Have you been diagnosed with allergies before?
  • What are your symptoms?
  • Do you take any over-the-counter (OTC) medications to treat your symptoms?
  • When do you notice your allergies start to act up?
  • Do you have any pets?
  • How often do you vacuum your carpets, wash your bedding and clean other surface areas?


What tests will be done to diagnose environmental allergies?

Your healthcare provider may use different allergy tests to help diagnose your environmental allergies based on your symptoms and suspected allergens. These tests may include:

Skin prick (scratch) test

This test exposes your body to small amounts of specific environmental allergens.

Your healthcare provider will first clean a test area of your skin with iodine or alcohol. The test area is usually on your forearm or upper back.

Your allergist will use a thin needle (lancet) to prick your skin with 10 to 50 different possible environmental allergens. The lancet won’t go deep into your skin. You’ll only feel a tiny pinch, and you won’t bleed.

Some allergists may place droplets of possible allergens on your skin. They then use a lancet to scratch your skin lightly. The droplets will enter your skin through the scratch. You’ll only feel slight discomfort, and you won’t bleed.

Allergic reactions typically occur within 15 minutes of exposure to the possible environmental allergens. Reactions may include skin discoloration (red, gray or white) or raised, round spots called wheals that look like mosquito bites.

Your allergist will measure the size of your wheal and record what allergen caused the reaction.

A skin prick test takes less than an hour.

Blood (IgE) test

During a blood test, your healthcare provider will use a thin needle (21 gauge, slightly smaller than the size of a standard earring) to withdraw a small amount of blood from a vein in your arm. The blood sample goes to a laboratory. The lab adds allergens to your blood sample and measures the levels of IgE antibodies in it.

It may take a week or longer to get the results from a blood test sent to a lab.

Blood tests can have a higher rate of false-positive results. A false-positive result is when a test says you have a specific allergy, but you don’t.

Management and Treatment

How do you get rid of environmental allergies?

You can’t get rid of environmental allergies, but you can take antihistamine medications to treat your symptoms.

What are the side effects of antihistamines?

Antihistamine side effects depend on whether you take first- or second-generation antihistamines. The U.S. Food and Drug Administration (FDA) approved the use of first-generation antihistamines in the 1930s. Examples of first-generation antihistamines include:

First-generation antihistamine side effects may include:

  • Drowsiness.
  • Dry mouth.
  • Dizziness.
  • Headache.
  • Cough.
  • Nausea and vomiting.

Second-generation antihistamines cause fewer side effects than first-generation antihistamines, including drowsiness. Examples of second-generation antihistamines include:

Second-generation antihistamine side effects may include:

One study reported increased anxiety and depression in people who took the antihistamines cetirizine and hydroxyzine. However, studies haven’t explored the effects of all antihistamines on mood disorders.

How soon after treatment will I feel better?

Antihistamines start to work about 30 minutes after you take them. They’re most effective within the first few hours.

Your healthcare provider may recommend that you take antihistamines every day to prevent symptoms.


How can I prevent environmental allergies?

A fluticasone nasal spray (Flonase®) is the gold standard for preventing moderate to severe environmental allergy symptoms, including congestion, postnasal drip and sinus pressure. These medications work by decreasing inflammation in your nose. You may need to use nasal sprays every day to prevent environmental allergy symptoms. Side effects may include nasal irritation and nosebleeds. Regular nasal spray use in people over 65 may cause eye pressure (glaucoma), so it’s a good idea to talk to a healthcare provider before use.

Taking second-generation antihistamines daily is the best choice for mild allergies.

The following tips can also help you avoid allergy symptoms:

At home

  • Keep your windows closed and use air conditioning. Keeping your windows closed helps limit the amount of pollen entering your home. It’s best to avoid using window fans. Fans can cause pollen and dust to enter the air, making it easier to breathe.
  • Filter the air in your home. Cover your air vents with cheesecloth to filter pollen. It’s also a good idea to use a disposable high-efficiency particulate air filter (HEPA) if you have a forced-air furnace. Be sure to use filters with a high filtration rating and change them regularly.
  • Reduce humidity in your home. Keep the humidity in your home below 50% to prevent mold growth and dust mite reproduction.
  • Avoid moldy areas. These areas may include basements, garages, crawl spaces, barns and compost heaps. Clean these areas often, if possible.
  • Regularly brush and bathe your pets. Don’t allow them in your bedroom or on your furniture.
  • Avoid dust mites. Use microfiber covers on your pillows, mattresses and box springs. Wash your bedding every week in hot water (130 degrees Fahrenheit (54.44 degrees Celsius). Avoid overstuffed furniture or bedding and pillows stuffed with feathers (down). Dust mites can easily enter these materials. Leather and vinyl furniture are best because dust mites can’t enter these materials.
  • Vacuum rugs, carpets and other surfaces regularly. It’s a good practice to vacuum at least twice a week. Consider wearing a mask when you clean. If possible, consider replacing wall-to-wall carpet with tile, wood, linoleum or another hard surface that dust mites can’t enter. If you have area rugs, it’s best to vacuum and wash them regularly.
  • Don’t smoke indoors. Use tobacco products, marijuana, scented candles outside and any other products that produce smoke outside.


  • Keep your windows closed while driving. Use your air conditioner and set it to recirculate the air.
  • Check the pollen count before spending time outside. Stay indoors as much as possible on hot, dry, windy days. Try to stay indoors between 5:00 a.m. and 10:00 a.m., when pollen counts are usually the highest.
  • Wear a mask. Wear a mask while mowing the lawn, raking leaves, gardening and working with hay and mulch.
  • Bathe after spending time outdoors. Wash your hair and change your clothes to remove pollen.
  • Dry clothes in a dryer. Don’t hang clothes or linens outside to dry. They may collect pollen and molds.

Outlook / Prognosis

What can I expect if I have environmental allergies?

You can’t cure environmental allergies, but you can manage the symptoms by avoiding allergens and taking medications.

Living With

When should I see my healthcare provider?

See a healthcare provider if you regularly have allergy symptoms, especially if they affect your day-to-day quality of life.

What questions should I ask my healthcare provider?

  • How can you tell that I have environmental allergies?
  • What specific allergens are causing my allergy symptoms?
  • What allergy medications do you recommend?
  • What’s the complete list of side effects of your recommended allergy medication?
  • Should I take allergy medications every day or only when I develop symptoms?
  • Can I still spend time outside?
  • Are there any plants I should avoid having in my house or yard?
  • How do I know when I have allergy symptoms or cold and flu symptoms?

Additional Common Questions

What is the difference between an environmental allergy and a food allergy?

An environmental allergy is when your immune system overreacts to allergens in the environment.

A food allergy is when your immune system overreacts to the proteins in specific foods. Common food allergens include milk, eggs and peanuts.

A note from Cleveland Clinic

Environmental allergies occur when your immune system mistakenly triggers a defensive response to certain substances in your environment. This response — or allergic reaction — can cause various symptoms, including congestion, watery eyes, a runny nose and fatigue. If you have environmental allergy symptoms, reach out to your healthcare provider. They can conduct tests to determine what allergens are triggering your allergic reactions. They can also prescribe medications that prevent allergy symptoms.

Medically Reviewed

Last reviewed on 04/25/2023.

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