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This article outlines the basic indoor air quality and asthma-related concerns from animal allergens (dogs, cats, other animals), recommends actions, and cites authoritative sources for more in-depth reading. According to the US EPA and other expert sources, [paraphrasing document cited below] animal skin flakes, urine, feces, saliva, and hair can trigger asthma or other allergic reactions.

At ALLERGENS in BUILDINGS, RECOGNIZING we discuss and provide photos of common indoor allergenic particles found in homes and in the work place. Also see CAT DANDER in buildings. At ALLERGEN TESTS for BUILDINGS we discuss testing buildings for the presence of animal allergens or other allergens such as insect fragments or fecals. Also see  ANIMAL ODORS IN BUILDINGS for suggestions about removal of pet odors.

Dogs, cats, rodents and other mammals can trigger asthma/allergic reaction in people who have an allergy to animal dander. Proteins in these materials have been reported to sensitize people and can cause allergic reactions or can trigger asthma episodes in people who are already sensitive to animal allergens. The most effective method to control animal allergens is to remove the animal from the building, followed by thorough [professional] cleaning. I also discuss the effectiveness of various strategies for keeping your pet in a home with someone who has asthma or pet allergies.

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PERSISTENCE OF ALLERGENS: Persistence of Animal Allergens & Animal Dander or Animal Hair in the Indoor Environment

Animal dander in homes is a common source of respiratory irritants associated with asthma and allergies. Animal dander, hair, and other organic debris in homes can also result in a significant increase in the level of dust mites, mite fecals, and other allergenic insect parts and fragments.

These two lab photos of human skin cells, animal skin cells (dander), and other debris are typical of a home where pets have been resident. The left photo includes a feather barbule fragment and insect fecals. The right photo shows skin cells and animal dander.

Signs of "hidden" animal presence: We often find evidence of other animals who have been frequently present in a home even though the human occupants didn't know it - either because the animal was the pet of a prior owner (Chinchilla hair at above left) or a nocturnal visitor to the food bins (mouse hair at above right). Finding evidence of animals might mean that additional cleaning is needed to remove their remaining allergenic particles.

The U.S. EPA indicates that allergens are found months after a pet (or mouse problem) has been removed.

Our particle studies in homes with pets show that although a dog or cat who is never allowed out of the basement will concentrate its hair and dander at that level, I will find the animal dander and hair at all floors and in every room of the home.

We often find significant levels of allergens in buildings where the source animal(s) have been gone for years if professional cleaning has not been performed. Even when cleaning is thorough I can find allergen materials remaining. In fact, I find some levels of animal dander in most homes, even if the home has never housed a pet, and in homes where a previous owner had pets, the dog or cat dander is often among the most frequent particles found in our samples.

While careful and thorough cleaning after animal removal is usually successful at removing the bulk of allergenic particles, for people who are extremely sensitive even low remaining allergen levels may be a problem, particularly if stirred or distributed by non-HEPA vacuuming and dusting, by the operation of HVAC equipment, ceiling fans, whole house fans, or other sources of indoor air movement.

More suggestions for dealing with pet allergens in the home are in this document at the links at left.

CLEANING SUGGESTIONS For Buildings Previously Occupied by Animals/Pets

After removing the pet or pest animal(s), the following measures are recommended: thorough professional duct cleaning, commercial steam cleaning of some materials, dry-cleaning or very hot water laundering of clothing, freezing of small items (to kill dust mites), washing and HEPA vacuuming of interior surfaces. Note that ordinary vacuum cleaning is not effective and may make matters worse for sensitive occupants as it causes allergenic particles to become airborne.

Animal dander particles can be less than 1 micron in size and thus may remain airborne for more than 8 hours after vacuuming.

Many sources offer advice aimed at keeping a pet in the home: keeping pets out of bedrooms and other sleeping areas and keeping these areas isolated from pet-occupied areas, keeping pets away from fabric-covered furniture, frequent washing of pets, frequent house cleaning using the extensive means described above are all listed.

More suggestions for dealing with pet allergens in the home are in this document at the links at left.

Drug Medication vs. Building Cleanup as Treatment for Asthma Reaction to Animals Indoors

No expert sources other than drug suppliers cite using medication as the first choice in addressing pet allergies. On the other hand, most expert sources I surveyed agreed that "...the most effective method to control exposure to animal allergens is to keep your [building] pet [and animal-pest] free."

ANIMAL DANDER STUDY: Animal Dander Advice: Environmental Study Report Text

The following is our standard advice included in indoor air quality investigations when I find a high level of animal dander in a building, regardless of whether it's cat, dog, other pets, or other animals.

Animal Dander: According to the US EPA and other expert sources, [paraphrasing document cited below] animal skin flakes, urine, feces, saliva, and hair can trigger asthma or other allergic reactions. Dogs, cats, rodents and other mammals can trigger asthma/allergic reaction in people who have an allergy to animal dander. Proteins in these materials have been reported to sensitize people and can cause allergic reactions or can trigger asthma episodes in people who are already sensitive to animal allergens.

The most effective method to control animal allergens is to remove the animal from the building, followed by thorough [professional] cleaning. The EPA indicates that allergens are found months after a pet (or mouse problem) has been removed. I often find significant levels of allergens in buildings where the source animal(s) have been gone for years if professional cleaning has not been performed. Even when cleaning is thorough I can find allergen materials remaining.

While adequate cleaning after animal removal is usually successful, for people who are extremely sensitive even low remaining allergen levels may be a problem, particularly if stirred or distributed by HVAC equipment or other sources of air movement.

After removing the pet or pest animal(s), the following measures are recommended: thorough professional duct cleaning, commercial steam cleaning of some materials, dry-cleaning or very hot water laundering of clothing, freezing of small items (to kill dust mites), washing and HEPA vacuuming of interior a surfaces. Note that ordinary vacuum cleaning is not effective and may make matters worse for sensitive occupants as it causes allergenic particles to become airborne.

Animal dander particles can be less than 1 micron in size and thus may remain airborne for more than 8 hours after vacuuming.

PETS AS FAMILY MEMBERS: What to do If Your Pet is a Family Member

Some people with allergies and even asthma (and of course others without these complaints) have pets who have become such a loved family member that "getting the animal out of the house" is not something they're not willing to consider. Some of our clients have taken this position and stuck with it until the sufferer's asthma became acute. When I was a boy, and was terribly allergic to cats, we had them in our home anyway.

We loved our cats and played with them constantly, with running eyes, sneezing, and a runny nose the whole time. Luckily for me it was a childhood allergy that I outgrew, or perhaps became immune-to. Some remarkable studies have shown that living in a very sterile environment increases our vulnerability to some diseases and allergies. Farm kids who are exposed to enormously higher levels of allergens than city kids, have a much lower incidence of asthma. If you're allergic or asthmatic you should discuss these concerns with your doctor and should be candid about your exposure and your intentions regarding the pet.

Restricting a pet to only certain rooms or floors in a house might reduce the allergen level in some areas but it may not reduce it enough to alleviate suffering for anyone who is sensitized. Furthermore this is not the happiest life for a pet to live in the basement away from its family.

REDUCING PET ALLERGENS: How to Reduce (somewhat) Exposure to Pet Allergens

What else can you do to reduce the indoor animal dander problem in a home with asthmatics or allergics? These suggestions are roughly in order of importance and effectiveness, in the author's opinion, with some consideration given to ease of implementation.

Frequent house cleaning including damp mopping or HEPA vacuuming will not cure this problem but will reduce the particle levels

Eliminate indoor carpeting. In buildings with wall to wall floor carpeting or large area rugs, our indoor particle studies show that these floor coverings form an inexhaustible reservoir of allergens including the original animal dander from pets which no amount of vacuuming or "carpet cleaning" will remove completely. Depending on the historic indoor moisture levels, quite often I also find that dust mite fecals, another very common indoor allergen, are at much higher levels in homes with pets. More pets or larger pets, shedding more dander and thus feeding more mites, produce higher levels of mite fecals in indoor dust.

HEPA vacuum cleaners, especially units that do not have significant air leaks when the vacuum is running, do not stir up as much airborne debris, allergens and other particles, as ordinary vacuum cleaners. But before buying an expensive vacuum cleaner, further evaluation of the leakiness, operating cost, and bag or filter changing convenience should be made. I collect data on vacuum cleaner effectiveness but this work is not ready for release. When it is I'll post it at this website.

Central Vacuum Systems, if properly installed, vent directly outside, avoiding the issue of stirring up indoor particles during house cleaning. It's a more-costly but great idea. Just be sure the vac is properly vented. I've inspected homes at which the central vacuum machine was in a laundry room or basement, venting its dust back into the home.

Humidity control: is a step more critical than may be obvious. In homes with high humidity, of which the most egregious case is a carpeted damp or wet basement, the level of dust mite and other insect fecals (including carpet beetles and other mites) skyrockets. In homes with a high level of animal dander these animal skin cells form a feast for dust mites.

When we investigate the air and dust in buildings which have a combination of a high level of animal dander, carpeting, and high humidity, these three strikes against indoor air quality are a strikeout for asthmatics and people with allergies. Keep the humidity low enough to discourage dust mites (45% to 55%, with a lower target for problem areas like basements and crawl spaces) and fix gutter/downspouts, plumbing leaks, or other sources of indoor moisture.

Also see What indoor humidity should we maintain in order to avoid a mold problem?

Air filtration by HVAC equipment can substantially reduce indoor airborne particle levels if the equipment is designed for that purpose, including cascaded air filtration and continuous fan operation.
More Reading: For a description of this approach, see Air Conditioning System Blower Fans & Filters Cascading for Optimum Indoor Air Quality

Pet Care: our cat sheds like crazy in the spring. Frequent brushing makes a difference in how much cat hair is distributed in the house. Also larger animals, particularly dogs, bring in a lot of dust and debris from outside, adding to the particle and possibly allergen indoor load - but then, this is arm-waving opinion, not science.

Air Purifiers: none of the portable indoor air "purifiers" on the market (May 2006) is very effective at reducing the overall indoor airborne particle level in buildings, despite claims, and in some cases, poorly designed studies which may say otherwise. I have measured dust and air in homes which in some cases had several such devices operating in each room. There was no obvious correlation between use of this equipment and a reduction in indoor particle levels except when the equipment was operated in a small room which has its windows and doors kept shut, has no wall to wall carpeting, and has an absolute lack of clutter, leaving smooth, easily cleaned surfaces and little fabric, curtain, or other materials to act as particle reservoirs.

Ozone Generators: a dog expert who sometimes boarded up to 15 dogs in her home spent a good part of her life cleaning. Nonetheless the level of dog dust and dander was astonishing, penetrating even the walls and attic of the building. After a decade of this craziness we didn't need IAQ instruments and surveys to see the layer of thick brown dust on the attic insulation and even in wall cavities around any penetration such as at electrical outlets.

The dog girl ran an ozone generator in an effort to reduce dog odors and dust in the home. Not only was the ozone unable to make much of a dent in this debris, it was potentially dangerous. Another of our clients destroyed their home by overdosing it on ozone using a commercial ozone generator which oxidized their carpet padding and other building components. Ozone for pet dander control is a bad idea.

More Reading on Indoor Allergen Reduction & Control:

• CAT DANDER CLEANUP, PREVENTION - how to clean up cat dander in buildings and prevent its movement among building areas where cats remain
• The Use of Ozone Indoors for Control of Odors and Mold Removal in Buildings: A Summary of Hazards and False Claims.

At the end of the day, while we have verified that creating an anti-dust, hard surface, no-clutter environment, combined with regular cleaning and pet restrictions (no dogs in the bedroom), if there are animals in the home there will be animal dander throughout the home, moved there by the combination of shedding animals, moving air, and moving people.

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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY

AIR POLLUTANTS, COMMON INDOOR
ALLERGEN TESTS for BUILDINGS
ALLERGENS in BUILDINGS, RECOGNIZING
ALLERGY TESTS for PEOPLE
ALLERGY TEST ACCURACY
ANIMAL ALLERGENS / PET DANDER
  PERSISTENCE of ALLERGNS
  CAT DANDER in BUILDINGS
  CLEANING SUGGESTIONS
  DRUGS vs CLEANUP
  ALLERGEN DANDER STUDY
  PETS AS FAMILY MEMBERS
  REDUCING PET ALLERGENS
ANIMAL ENTRY POINTS in BUILDINGS
ANIMAL ODORS IN BUILDINGS
  Finding the Source of Animal Odors
  Cleaning Suggestions for Odors / Urine
  Removing Odors at Building Exteriors
  Removing Urine Odors from Clothing
BASKETBALL MOLD SYNDROME - BBMS

BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
BIOGAS PRODUCTION & USE

BIOLOGICAL POLLUTANTS
BIOLOGICAL POLLUTANTS in the HOME - EPA
Bisphenol-A, BPA

BLACK MOLD, HARMLESS COSMETIC
BLACK MOLD, TOXIC & ALLERGENIC

BOOK MOLD, Moldy Book Cleaning
BOOKSTORE - ENVIRONMENTAL
BUYERS GUIDE - home inspections for mold
CAT DANDER in BUILDINGS
  WHY TEST FOR CAT ALLERGENS
  HOW TO INSPECT TEST for ANIMAL ALLERGENS
  FORENSIC APPROACH TO CATS
  CAT DANDER CLEANUP, PREVENTION