Combating Indoor Allergies


Outdoor allergies are quite common and well known. Most are commonly called "hay fever." Pollens from various plants, trees, grasses and weeds can be common triggers for allergy symptoms. So what about when you are indoors and less directly exposed to these plant by-products?

There are some allergens that you might become exposed to outside as well as inside, but generally exposure inside is more concentrated due to the enclosed nature of the environment.


Dust mites live on dander, or sloughed off skin from humans or animals. They also eat some molds. Dust mites tend to be abundant in crowded and humid environments. The crowd provides the food and humidity provides the water. They find plenty of hiding places in fleecy material. Dust mites cannot live in dry climates and will die off when humidity falls below 40%. But even after they die the problem persists until the body parts and droppings are removed.

Bedrooms are especially favorable habitats for dust mites. Food supplies are generally plentiful. Most people spend an average of eight hours in a horizontal position and thus rub off a relatively large amount of skin. Mattresses, bedclothes, carpets and other fleecy materials can become infested. Even if the humidity is generally low, some dust mites might obtain sufficient moisture from humidity generated by exhaling and from sweat.

Is it an allergy or just a cold? If you have symptoms for more than a couple of weeks and if they include itchy eyes and nose. Plus if your nose drips with thin clear liquid, it's probably an allergy.


Discounting pollens, what are the potential allergens inside? One of the most commonly named allergy trigger is dust. But saying you are allergic to dust doesn't tell us much. Keep in mind that "dust" isn't just fine particles of dirt. Dust will be made up of virtually anything in the house that can become airborne and then settle out. In addition to irritants like fiberglass and construction dust, numerous allergens can also be present. Insect parts and debris including that of dust mites and cockroaches are often found. Fungal (mold) spores and hyphae (underlying fungal structure) are not unusual components. And the most plentiful potential allergen is usually dander, which could be shed by human and/or animal. All sorts of protein material might be present in a somewhat catchall item called "organic detritus" which is described as partially decomposed material of organic origin. Interlopers like rats and mice also produce allergens in their urine, feces and dander.


So what can be done about this ocean of allergens? There are certain general steps that can be taken to reduce exposure.

  • Reduce the amount of dust by vacuuming often with a HEPA (High Efficiency Particulate Arresting) vacuum cleaner. Dust with damp cloths or with cloths using cleaners for collecting dust. Also thoroughly vacuum any fabric-covered furniture, i.e. chairs and couches.
  • Use good filtration in your HVAC system and change them regularly. At a minimum the filters should be pleated, which gives more surface area to better trap particles. The wispy flat filters help protect the moving parts of the machine, but do virtually nothing for air quality. HVAC systems should be thoroughly cleaned every five to eight years based on their use and environment.
  • In locations where you spend the most time, especially bedrooms, using a HEPA filtered air purifier can be helpful.
  • Keep humidity below 50% using a dehumidifier as necessary. Like all animals, dust mites require food and water to survive. Their major source of food is skin flakes (dander). They derive their moisture from high humidity. Below 50% or even closer to 40% is not a conducive environment for dust mites.
  • Keep a close eye out for water intrusion, like "popped" nails on walls, water stains, or baseboards that are swollen or pulling away from the wall. These are possible locations of mold growth inside the wall.v
  • Additional actions to avoid exposure to dust mite allergens include removing carpeting and as much fleecy material as possible from the bedroom. Such locations are nice snug abodes for these little critters. Wash all bedclothes regularly in very hot water. There are also hypoallergenic vinyl or plastic covers that can be used to cover mattresses and pillows.
  • If you find you are allergic to your dog or cat, it's probably not a good idea to sleep with them, or to have them in the bedroom.
  • Finding out specifically what you are allergic to should help you to customize the actions you can take to avoid your particular allergy triggers.

Allergies can be unpleasant additions to your life, so knowing and applying actions to avoid exposure can bring great relief.

  Steve Huff
Senior Indoor Air Quality Investigator