Indoor Allergy Triggers

Discover what’s behind your symptoms.

Medically Reviewed by Brunilda Nazario, MD on March 11, 2009
Written by Wendy C. Fries
5 min read

You come home after a day away, step into the house, and the symptoms hit: Watery eyes, scratchy throat, congestion. Could it be indoor allergies?

Allergies are very common. An estimated 50 million Americans are allergic to everything from dust and dander, to mold and mites.

But what about you? How can you be sure you have indoor allergies -- and pinpoint what’s causing them? To help you understand what’s behind your allergy symptoms, WebMD got tips from experts on how to recognize common allergy triggers and get the right diagnosis.

Half the battle of treating indoor allergies is recognizing you have them, says allergist Asriani Chiu, MD, associate professor of pediatrics and medicine (allergy/immunology), in Wisconsin. Allergy symptoms can be hard to pinpoint because they often mimic cold symptoms. Yet there are differences.

Typical indoor allergy symptoms include:

  • A drippy nose with watery, clear secretions
  • Itchy eyes
  • Symptoms that linger for weeks

Cold symptoms differ in a few crucial ways, including:

  • Nasal secretions are discolored (yellow or green)
  • You have chills and body aches
  • Symptoms linger a week or 10 days

It also helps to understand the most common indoor allergy triggers.

Every home harbors potential allergens, from the rare to the ubiquitous, but these five are the most common triggers for indoor allergies:

  • Dust: Dust can be made up of dozens of things, including tiny bits of plants, skin, soil, insects, food, fibers, and animal matter. Any one -- or more -- of these minute substances could trigger indoor allergies.
  • Dust Mites: As you may have guessed, dust mites thrive on dust. And, dust mite droppings are the most common trigger of allergy and asthma symptoms, according to the American Academy of Allergy, Asthma, & Immunology. Although you’ll find dust mites all over the house, they concentrate in areas rich with human dander (dead skin flakes) and high humidity: bedrooms, carpets, bathroom rugs.
  • Mold: Mold and mildew thrive in high humidity, such as your steamy bathroom or chilly, damp basement. Once they take hold, mold and mildew shed tiny spores -- and these spores trigger indoor allergy symptoms.
  • Pet Dander: If you have pet allergies, you’re not actually allergic to cat or dog hair. Instead, the allergic reaction is caused by a tiny protein in an animal’s saliva. Even homes without pets may contain dander. That’s because pet dander is sticky and light. It clings to clothes, shoes, and hair. Thus, pet dander can be found in boardrooms and classrooms, as well as at home.
  • Cockroaches: Like dust, roaches can be found almost everywhere. As with pets, it’s not the roach itself that triggers indoor allergies. Instead, the potential allergen is a protein found in the cockroach’s droppings.

Dander, droppings, dust -- if every home has them, how can you narrow down what is triggering your indoor allergies? There are essentially two ways: By trial and error, and through allergy testing.

For the trial-and-error approach, searching for patterns is key, Chiu tells WebMD. Perhaps you visit your sister and their cats every Monday. Before long you notice every Monday that you’re blocked up, blowing your nose, and rubbing your eyes. It doesn’t take long for this flash of insight: You’re allergic to cats.

Of course, discovering what’s triggering your indoor allergies isn’t always that easy. Which is why “the best way to find out what you’re allergic to is to see an allergist,” says Alan Goldsobel, adjunct associate clinical professor at Stanford University Medical Center, and spokesman for the American Academy of Allergy, Asthma & Immunology.

An allergist can cut through the guessing games with examinations and tests, zeroing in on what’s behind your indoor allergy symptoms, Goldsobel tells WebMD. Allergists generally diagnose allergies in three ways:

  • Personal and medical history: Through questions about your personal and medical history, an allergist will note your symptoms and narrow down their possible causes.
  • Examination: To further determine symptoms and causes, an allergist will also perform a physical examination, paying special attention to your eyes, nose, throat, chest, ears, and skin. Test may also include X-rays of your lungs or sinuses.
  • Skin, patch, or blood tests:For many people, skin tests are the most accurate and least expensive way to confirm suspected allergens, according to the Asthma and Allergy Foundation of America. Results can take as little as 20 minutes, and generally show up as redness, swelling, and itching at the site of the scratch or needle prick.

With patch tests, the doctor places a potential allergen on your skin, covers it with a bandage, and checks your reaction 48 hours later. If you develop a rash, you’re allergic to that particular allergen.

Blood (RAST) tests are used when skin testing isn’t possible, such as when people are taking certain medication or have a skin condition. Your allergist will take a blood sample and send to the lab. The lab adds the suspected allergen to the blood sample, and measures how many antibodies your blood makes to attack the allergen.

Although there isn’t yet a cure for indoor or outdoor allergies, there are ways to manage them once you know your triggers. The three main approaches to treating indoor allergies include:

  • Avoiding indoor allergy triggers.

“Avoidance is the best way to treat any allergies,” says Chiu. That means avoiding exposure to as many allergens as possible. If you are allergic to your cat, for example, you may ban Fluffy from the bedroom. Or, if you have a dust mite allergy, you may remove the carpet and upholstered furniture, spots where dust mites thrive.

  • Controlling the allergy environment.

Perhaps you don’t want to tear up the carpet or banish beloved pets. Key tips for managing indoor allergies include cleaning; lowering your home’s humidity; and minimizing contact with allergens. For example, encase pillows and mattresses in allergen-blocking bedding.

  • Seeking medical therapy.

Medical treatment for allergies includes controlling indoor allergy symptoms through medication, allergy shots, and home therapies like nasal irrigation. Allergy shots in particular can be very effective at dealing with indoor allergies, says Goldsobel.

It may take time to discover the allergens that trigger your indoor allergies, but the results are worth the effort. Knowing your triggers is the key to managing -- and even preventing -- indoor allergies symptoms day and night.