Everything You Need To Know About Indoor Allergens

I’ve had many of the typical signs of allergies for most of my life. You know, the itchy, swollen, watery eyes, the sneezing.  I’ve learned that it’s important to understand the most common indoor allergens and their sources, so that you can prevent and treat any symptoms and allergic reactions.

What Are Indoor Allergens?

Allergens are the agents distributed through the air that cause allergic reactions. They settle onto the floors and the furniture. They are so tiny they have to be measured in micrometers, or microns. Allergens are found everywhere in the world – and there’s no escaping them. You wouldn’t believe the gross things that we all breathe in daily.

The immune systems of allergy sufferers are sensitive to allergens and consider allergens to be foreign invaders that must be fought.

These sensitized immune systems cause a series of responses that result in chemical releases (mediators), such as histamine. The mediators affect cells and tissues in a certain way, and that is what causes the various allergy symptoms.

Outdoor allergens, such as pollen, are what people commonly think about when they talk about allergens or allergies. But there are many types of allergens that are commonly found indoors as well. In fact, homes can contain more allergens in the air than outside air, especially because they can easily become trapped indoors.

Nearly 50 million Americans suffer from indoor allergies. They are caused by things like pet dander, dust, mites, mold, and so on. We can reduce allergy symptoms by reducing our exposure to household allergens. That is done by creating better air quality in all of the indoor spaces where we spend the most time.

The Most Common Indoor Allergens

There are many allergens, but just four of them, according to medical doctors are the main allergens that cause allergic reactions. These are dust mites, pet dander, mold and cockroaches. All four of them are found in the dust that is in the air we breathe.

The following video from the American Academy of Allergy Asthma and Immunology (AAAA&I) and goes into detail on the top two most common indoor allergens – dust mites and pet dander.

Here is a broader list of the most common indoor allergens:

  • Dust – Dust is made up of things like animal matter, hair, fabric fibers, dust mites, food, insect fragments, soil particles, skin, plant bits, mold spores and many other things. What is in your home’s air has a lot to do with the things that you keep in your home. What is in the outdoor air that surrounds your home also creeps in one way or another. Subjected to airborne dust, you can develop allergy symptoms from any one of the many allergens found in there.
  • Dust Mites – These little bugs love to feast on dust and human skin flakes. In fact, the American Academy of Allergy, Asthma and Immunology says dust mites are the most common trigger of allergy symptoms. These bugs thrive in warm, humid places. Unlike bed bugs, they don’t bite you. You would only suspect they are there when your indoor allergies symptoms get bad.
  • Pet Dander – Pets with either feathers or fur have dander that are allergens. Dander is essentially dead skin cells, but the allergic reaction comes from the protein found in the pet’s saliva. For some unknown reason, some dog breeds, such as Portuguese Water Dogs and Poodles, cause less symptoms than other breeds do. It may be that they produce few proteins.
  • Mold – Mold and mildew grow in damp places like the bathrooms, the basement, and on house plants. It’s the spores they shed that trigger indoor allergy symptoms.
  • Cockroaches – Yup. We actually breathe in dead roach particles. The allergens come from protein in their feces. If I didn’t already have an air purifier, I’d be online ordering one right now after reading that news. Cockroaches are more of a problem in the southern part of the United States and in cities.
  • Pollen – It’s not actually an indoor allergen except for the fact that both humans and pets bring it in from the outdoors and spread it around. Some people think they are allergic to their pet when they allergic to the pollen that the pet got on her when she was outside and then brought into the house.
  • Cigarettes – This is an allergy irritant rather than an allergen. Cigarettes greatly affect asthmatics too.

The following video from the AAAA&I provides some more detail around the other common indoor allergens, including mold and pests.

Sources Of Indoor Allergens

These invaders of our space and our health need to be evicted. We must first keep in mind the sources of allergens – where they come from and hide. You’ll find them in the following places:

  • Bed linens – Like bed bugs, dust mites love to share your bed with you. They love the dead human skin and other dust particles that they find in them.
  • Mattresses and pillows – Dust mites live in mattresses and pillows for the dust and dead skin that settle into those places too.
  • Soft, upholstered furniture – Dust mites share space with you in your favorite overstuffed furniture for the dead skin cells and dust lodged there.
  • Stuffed toys – Yup, dust mites love the fabric-based toys.
  • Carpets / rugs – Dust mites are hard to get out of carpets, which are another one of their favorite hangouts. And they really like damp bathroom throw rugs.
  • Damp areas – The damp places in our homes are home to mold spores (e.g., bathrooms, basements, kitchens).
  • Pets – Of course, pets are the source of pet dander. Pets also get pollen, another allergen, on their fur when they are outside, just like humans do on our clothes. Pets and humans then bring that pollen indoors and spread it around.
  • Indoor plants – Mold spores can form on indoor plants, especially with over watering or damp soil.
  • Surface tops – Whatever allergens are floating around in the air that don’t get breathed in by a living being, sucked in by an air purifier, or blown out a door or window eventually settles onto surface tops. Surface tops are technically anything beneath the air, but we think of things like countertops, tables, picture frames, lamp shades, and so on.
  • Air – Ultimately, air is where our indoor allergies come from. It is where all the players – the allergens – are that we breathe in. We’re talking parts of dead bugs, skin flakes from humans, dander (pet skin flakes), cigarette smoke, other smoke, mold spores, dust mites, dirt, pollen, and others.

Most Common Symptoms Of An Allergic Reaction

Cartoon of Allergy Symptoms

It’s important to know that what we may think is a cold can actually be an allergic reaction. Time usually tells the tale because a cold will eventually go away, but an allergy will hang on for a while until you remove the irritant. You can treat your condition if you know which it is.

In general, indoor allergies can bring on:

  • Runny nose, itchy nose, stuffed-up or post-nasal drip
  • Sneezing
  • Watery, itchy or swollen red eyes
  • Headaches
  • Rash or eczema
  • Coughing or wheezing
  • Scratchy, swollen throat
  • Tight chest

How To Treat An Allergic Reaction To Indoor Allergens

In addition to controlling the allergens in the home environment through thorough cleaning and taking other preventive actions, you can irrigate your nasal passageways at home.

You can also get help from healthcare professionals, who can offer you:

  • Allergy immunotherapy
  • Allergy shots
  • Steroids
  • Decongestants
  • Antihistamines

The allergy shots are quite effective for relieving indoor allergy symptoms, according to Stanford University Medical Center adjunct associate clinical professor, Alan Goldsobel.


To manage allergens in our home, we must systematically control our environment.

Mold is an allergen that loves humid environments. Therefore, using a dehumidifier that will take the relative humidity in your home down to at least 40% can help a lot. That is a humidity level dust mites won’t like either. You can also clean all mold that you see with bleach. Don’t forget to properly ventilate and protect your respiratory system when you work with bleach. The Environmental Protection Agency recommends that you need to regularly ventilate your home.

Wipe the dog down when she comes in (and change your clothes when you come indoors) during pollen season. Using an air purifier that has a true HEPA filter on it will take around 80% of the pollen out of your home’s air. Keep the windows closed during pollen season and when it is humid outside.

If you have a dog, it is smart to have your little fur ball bathed fairly often. If she has long hair, you may also want to keep her hair trimmed. Have a family member who is not allergic to dog dander drop Fluffy off at a dog grooming place for a total makeover. Fluffy will come back later on with the allergens washed away somewhere else, by somebody else, and her shorter hair will be less of an allergen collection site. It wouldn’t hurt if somebody vacuums the car out at some point after hauling the dog around in it.

Regular vacuuming or carpets / rugs and any upholstered furniture can help keep dust mites in control. It’s also a good idea to to buy special allergen covers for your box springs, mattress, and pillows.

If the temperature in your home has stayed over 70 degrees and the humidity has remained over 40%, dust mites are very likely thriving in the bed linens and in the upholstery that skin comes into contact with often. In that case, you should put the dirty bed sheets into the washer. To kill the dust mites, you will need the water to be at least 130 degrees Fahrenheit. You will need to wash your sheets about every week or week and a half.

Mites are also in your throw rugs, carpets, heavy drapes, your kids’ stuffed toys, some of your dog’s toys, and other cloth-based places.

Vacuum the dust mites, flakes of skin, dust, and other nasties out of your mattress and pillows. Encase your box springs, mattress, and pillows with the new allergen covers. Do all of this for all of the beds in the house if there is more than one bed being used regularly.

Vacuum the upholstered furniture and the wall-to-wall carpeting. When you can afford to do so, buy yourself a certified asthma and allergy-friendly vacuum. Some of the special vacuums use water. Others use a double-layered bag or HEPA filter. Continue to vacuum the carpet once or twice every week. You could get rid of the carpet altogether if that is an option for you.

Stuffed toys contain both dust and dust mites. You could vacuum the dust off of them. To kill the mites, just put them into freezer bags and freeze them for three to four hours every week.

Wipe things down, including plants. Keep the surfaces uncluttered to help control dust mites. Use the appropriate cleaning agent wherever necessary. Dust off furniture with furniture polish. Wear a dust mask while dusting, then leave the house afterward to let the dust settle.

You could get cockroaches exterminated, though that is not the most healthy option for pets or for you. You can always use traps, boric acid, or poison baits to control cockroaches instead of chemicals if possible. And of course, it’s important to keep all garbage and food covered.

After this day or weekend of full-house cleaning, it will be a matter of maintenance. Clean everything, and find ways to distance yourself from sources of allergens whenever possible.


We’re all breathing in nasty things – and those things can make us feel sick and uncomfortable. Indoor allergies are no fun, but there are steps we can take to get them out of our homes and regain control of our indoor air quality and our health.

For more like this, check out our latest posts on Humidity Control (Humidifiers & Dehumidifiers) and Air Purifying.

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