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.
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.
Environmental allergies can affect anyone.
You’re more likely to have or develop environmental allergies if your biological parents have environmental allergies.
Environmental allergies are very common. Approximately 24 million people in the U.S. have environmental allergies.
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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.
Environmental allergy symptoms include:
Seasonal allergies can also trigger an asthma attack.
Environmental allergens include many different substances, including:
Examples of environmental irritants that cause non-IgE reactions include:
No, environmental allergies aren’t contagious. You can’t spread your environmental allergies to another person.
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:
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:
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.
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.
You can’t get rid of environmental allergies, but you can take antihistamine medications to treat your symptoms.
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:
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.
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.
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:
You can’t cure environmental allergies, but you can manage the symptoms by avoiding allergens and taking medications.
See a healthcare provider if you regularly have allergy symptoms, especially if they affect your day-to-day quality of life.
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.
Last reviewed by a Cleveland Clinic medical professional on 04/25/2023.
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