Allergens

By one estimate, allergies have a role in up to 95% of asthma cases.1 Of the different types of asthma, allergic asthma is the most common.2

When an allergen enters the airways of a person with asthma, it sets off a reaction that causes the airways to narrow. If you can avoid the things you are allergic to, you may have fewer asthma symptoms.3 Your airways will be less inflamed and you may need less medication.

Indoor allergens may be found throughout the house.4 For this reason, managing allergens in the home requires a multi-step process. This process may include some or all of the following: changes in bedding and bedroom flooring, frequent washing of bedding in hot water, use of HEPA-vacuum cleaners or HEPA air filters, and professional pest removal.

Pet Dander

Some people are allergic to the flakes of dried skin (called dander) and saliva from dogs and cats.3 Dog and cat allergy can develop over time.4 Cats and dogs produce different allergens. It is possible to be allergic to one species but not the other. People who keep their pets after becoming allergic may develop asthma.4 Continued pet exposure after developing asthma leads to worse asthma symptoms, and possibly asthma attacks.5

Interestingly, there is some evidence that infants (birth to three months) who live with dogs and cats are less likely to develop pet allergies.4 However, this has not been proven in high-quality studies. Getting a pet just to prevent allergies is not recommended.

How common are pet allergies?
In the United States, 33% of houses have cats and 40% have dogs.4 Homes with pets have more pet allergens than homes without pets. However, pet allergens are also found in homes, schools, and work places that do not have pets.3

Pet allergies are common.

  • Among older adults (ages 55+) with asthma, 26.9% are allergic to cats and 24.4% are allergic to dogs.6
  • Among younger adults (ages 20-40) with asthma, 40.5% are allergic to cats and 49.5% are allergic to dogs.6
  • Among a general population of 18 year olds, 20.5% are allergic to cats and 17.8% are allergic to dogs.7
  • In young children (ages 7-8) with asthma, 28.1% are allergic to cats and 27.3% are allergic to dogs.8

What can I do to reduce my exposure to pet dander?
The best way to reduce exposure to pet dander is to remove the pets from the house.3 Within 24 weeks of removing a cat from the home, allergen levels are the same as in a home that never had a cat.4 Taking extra steps to get rid of dander reduces allergen levels more quickly.

Of course, people love their pets. Removing the pet from the home may not be an option. Other ways to reduce pet dander are:

  • Keep the pet out of the bedroom and keep bedroom door closed.3,4 After removing the pet from the bedroom, use woven microfiber mattress and pillow covers. The covers limit exposure to dander that has already collected in the bedding.
  • Vacuum frequently with a HEPA vacuum.4
  • Dry dust hard surfaces with a sticky cloth.4
  • Remove carpeting or keep pets out of rooms with carpet.3,4 Dander tends to hide in carpet and is very hard to remove.
  • Do not sleep on upholstered furniture, such as couches.3 Dander collects on couches.
  • Consider using a HEPA air filter.4 These air filters reduce the amount of airborne allergens, but they have not been proven to improve asthma symptoms.
  • Consider washing your pet each week.3 Washing removes dander and dried saliva, so less accumulates in the house. However, studies have not shown whether this improves asthma symptoms.

There is little or no evidence that these steps will reduce asthma symptoms in allergic pet owners:

  • Getting a non-allergenic pet.4 Several cat and dog allergens exist, so no pet is certain to be non-allergenic for all people.
  • Getting a short-hair cat or dog.4 The length of hair has nothing to do with how allergenic the pet is.
  • Spaying or neutering your pet.4 There are good reasons to consider spaying or neutering your pet. Unfortunately, it is not clear how this will affect the amount of allergens your pet produces.
  • Sending your pet outdoors.4 Outdoor cats produce just as many allergens as indoor cats. Outdoor dogs produce fewer allergens than indoor dogs. However, homes with outdoor dogs still have higher levels of allergens than homes without dogs.
  • Air duct cleaning has not been studied well enough to recommend.3

Dust mites

Dust mites are tiny, eight-legged insects that live in house dust. Dust mite allergens are found in carpeting, bedding, upholstered furniture, and clothing, but rarely on hard surfaces.9 Allergic symptoms may worsen when the dust is disturbed, such as during cleaning or vacuuming. Dust mites can contaminate grain flour, causing a reaction in dust mite-allergic individuals.9 Skin prick tests can confirm a dust mite allergy.

How common are dust mite allergies?
About 80% of the US population is exposed to dust mites.3 Dust mites like humidity.9 Unless you live in the deserts of the Southwest or at high altitudes, you probably are exposed to dust mites.3 One study of children in New York City estimated that the 15.4% of children without asthma and 29.8% of children with asthma were allergic to dust mites.8 Even people with asthma who do not have a true dust mite allergy have fewer symptoms when they limit dust mite exposure.9

What can I do to reduce my exposure to dust mites?
Aside from moving to a drier climate, it is nearly impossible to completely avoid dust mites.9 Nevertheless, it is possible to reduce your exposure. This is done by reducing humidity and reducing the number of places dust mites can collect.

Several or all of these steps may be necessary to reduce your exposure to dust mites:

  • Use dust mite-proof (“allergen-impermeable”) mattress and pillow covers.3
  • Wash sheets, blankets, and stuffed animals in hot water (>130°F) weekly.3 Washing bedding in cooler water with detergent and bleach will also kill dust mites.
  • Reduce indoor humidity to less than 60% (30% to 50% is ideal). Dust mites require humidity to survive. Do not use swamp (evaporative) coolers or humidifiers.3
  • Vacuum frequently with a HEPA vacuum.9
  • Remove carpets and drapes from bedrooms.3,9
  • Remove other carpets that were laid on concrete.3
  • Do not sleep or lie on upholstered furniture, such as couches.3

Dry heat or freezing can kill mites, although it does not remove them. If you are allergic to dust mites, consider keeping flour, pancake mix, or other grain products in the freezer or refrigerator.9 Storing grain flours in sealable plastic bags can prevent dust mite contamination.

Room air filters may not be effective for removing dust mite allergens.3 Dust mite allergens are relatively heavy. They tend to settle on the ground instead of staying airborne.

Cockroaches
Some people are allergic to cockroach droppings and remains (called “frass”).3,10 Cockroach allergy can develop after a person is exposed to cockroaches.10 Once the allergy develops, having cockroaches in the home increases asthma symptoms and asthma attacks.5,10

Cockroaches are attracted to food and water. They prefer to hide in tight spaces. Your home could have cockroaches that you do not see. You can put out sticky traps to see whether you have cockroaches in your home.10

How common are cockroach allergies?
Cockroaches are most common in inner-city homes and in the southern parts of the United States.3 Sixty-three percent of homes have cockroach allergens.11 In 10.2% of them, allergen levels are high enough to cause breathing problems.11

In one study of people with asthma, 10.5% of older adults (55+) and 18.3% of younger adults (20-40) were allergic to cockroaches.6 In NYC-based study, 24% of children with asthma had a cockroach allergy.8

What can I do to reduce my exposure to cockroaches?
Eliminating the cockroaches is the first step in reducing your exposure:

  • Keep food out of the bedroom.3
  • Keep food and garbage in closed containers.3
  • Use poison baits, boric acid, or roach traps.3
  • Hire professional exterminators to use sprayed pesticides.10 The chemicals used to kill cockroaches may irritate your airways. If you do need to treat the home with chemical agents, ventilate the house and stay away until the smell has disappeared.3
  • Monitor for cockroaches using sticky traps.10

After the cockroaches have been removed, thorough cleaning is necessary to remove allergens left behind by the roaches:

  • Vacuum thoroughly with a HEPA vacuum.10 If the carpets cannot be thoroughly cleaned, they should be removed.
  • Remove cockroach infested mattresses.10 If this is not possible, use a mattress cover.
Written by: Sarah O'Brien | Last Reviewed: May 2016.
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