LARGER IMAGE - of this source of Cat dander and dog dander from pets living indoors can be a problem for people with allergies and asthma. Cat Allergies: how to inspect and test a building for current or past presence of cats, cat hair, cat dander, & cat allergens

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Cat allergen or cat dander testing:

This article discusses methods to check a building for animal allergens (cat, dog, etc) using as an example, Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens. . Hypo-allergenic - non-allergenic cat breeds.

We give in-depth information about indoor air quality problems: causes of respiratory illness, asthma, or other symptoms such as neurological or psychological problems, air quality investigation methods, and remediation procedures such as mold cleanup, handling toxic mold contamination, and building or mechanical system repairs.

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Cat or Dog Allergen Testing: Why Test for Animal Allergens Indoors?

Animal dander (C) Daniel Friedman

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The following question from a reader about testing for cat allergens in a home prompted our advice on what to do about cats and cat allergens which follows the cat question itself.

I am wondering if you know of or could perform a test in our home to determine the level of cat dander present. We are renting our home to tenants until next summer, but we have been told that the tenants may be keeping/hiding an indoor-only cat for their daughter (although our lease does not allow any pets).

Our daughter and I both have severe cat allergies and I do not know

(a) if we can prove that they have a cat and

(b) what if anything we could do after they move out to make the home safe for our daughter and me again. Do you have any suggestions?

How to Inspect for and Test for Previous or Current Animal Presence in a Building

There are several approaches I suggest to look for evidence of a cat (and cat allergens) in a building. A similar approach can be used to test for the presence of other animals: dogs, birds, and invading squirrels, mice, rats, raccoons, etc.

How to Test for Proof that a Cat is or has been in a Building - 6 Methods

Cat door (C) Daniel Friedman

Here are several easy and inexpensive approaches to testing for the presence of cats in a building:

  1. Visual evidence of cats in buildings: You see cats, cat litter box, cat bowls, or owners/occupants confirm that cats live or lived in the building. Even if no cats presently live in a building, there is often easy-to-spot visual evidence of prior cat occupants: a cat door (photo at left), fine and often deep cat scratches on furniture or trim, curtains, etc.

  2. The olfactory or "smell" test for cats: is there a cat-box odor somewhere? Especially in the case you cite, of an "indoor only" cat, a litter box must have been used in the building.

    Only the most diligent and frequent cleaning of the litter box and the surfaces around it will prevent any trace of a cat urine odor in that area. If a male cat was present in the building and has urinated or "marked" any surfaces, the smell will be very strong.

    Cats are generally clean animals provided the cat is healthy. But their litter box is a common odor source as well as a possible source of pathogens, bacteria, and mites.

  3. The animal hair test for cats: Most cats shed all the time. Somewhere in the building, in particular, where the cat likes to sleep or rest, there will be cat hair concentrated. (This is also a great place to sample for cat dander or cat "allergens"
  4. Cat dander in dust samples: cat dander, skin flakes shed by cats and other mammals, includes proteins (from the cat's saliva) which are allergenic and can be strong irritants to people with cat allergies or perhaps asthma. You can test for cat dander easily using a particle collection and identification approach:
    • Settled dust sample collection: collect one or more samples of settled house dust, particularly, in areas where a cat might have been spending a lot of time, or perhaps from an A/C or hot air furnace return register grille which is giving you a long term sample of house air.

      Use the adhesive tape sampling method at Six Easy Steps to Get and Mail a Mold Test Kit to a lab for 24-hour turnaround on sample analysis.

      Cat dander is visible on microscopic analysis provided the lab has a forensic analyst who is properly trained in animal dander identification. Photographs of cat dander are at our website too.
    • Vacuumed dust sample collection: an alterative which you may not be able to do as easily (I use special vacuum sampling equipment), is the collection of a vacuum sample of upholstered or carpeted surfaces in the most-suspect areas.

      A do-it-yourself dust vacuum approach has been used to sample dust on carpets and furniture, by using the open end of a vacuum cleaner tube covered by a special filter "sock" which can be purchased for that purpose.

      Some of our clients made their own particle collection sock using a square of fine linen (which loses some of the very small particles) or a coffee filter (which worked rather well provided the sample was not overloaded).

  5. Protein assay for cat allergens: There are also chemical assay procedures for animal allergen detection but in our opinion the particle identification approach is faster, less costly, at least as reliable if not more, and permits forming an opinion about the relative level of allergens by noting the dominant particles in the sample. A specific assay for a specific protein or chemical is not going to provide that contextual interpretative data.
  6. Use of a "black light" or UV lighting to check for animals in buildings can be a useful tool if you are screening for pet urine. We discuss this too further at  ANIMAL or URINE ODOR SOURCE DETECTION

Reader Question: Cat dander test kits? My downstairs neighbor's cat is driving me crazy. Could the cat dander travel up and in my unit like smells and odors? If

My new neighbor directly downstairs from me has a cat and I am afraid that it is making me sick. I live in a modern cement building however smells really travel between units through the windows due to airflow patterns.

So... Can cat dander travel up through one neighbors window and into another neighbors unit - even with screens on? I have not had allergy issues like ever and I am having severe allergic symptoms now and I have lived here for some time. Thanks - [Anon]

Reply: Cat dander particles are much larger than the smallest mold spores and more likely move through a building by mechanical means. Suggestions for reducing the level of cat dander in your apartment

Cat dander in the microscope (C) D Friedman

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with indoor air quality and building-related health complaints such as evidence of animal allergens or other problem particles, odors, or gases. Advice on how to decide whether or not you need a professional inspection and perhaps building testing for indoor air quality problems, their cause and cure, see MOLD / ENVIRONMENTAL EXPERT, HIRE ?

That said, here are some things to consider:

It is unlikely that a meaningful level of cat dander nor other similarly-sized particles would travel from a neighbor's window into another nearby apartment.

Certainly odors and gases from a nearby building or apartment might indeed be more noticeable, including perfume, cooking odors, MVOCs from a nearby mold contamination, and even odors from animals or animal urine if the problem reservoir is large and nearby and if the wind and air movement directions happen to move as needed.

Forensic Laboratory Approach to Identification of Cats in buildings

Cat hair (C) Daniel Friedman

An experienced analyst can express an opinion regarding the frequency of appearance of cat hair in a building dust or debris sample. Of course cat hair may have been visible and thick in a building.

Here we are discussing the presence of hair fragments in a sample where perhaps cat hair was not visually obvious at the building site.

Cat Dander (and animal dander in general) is Widespread

What do you "get" if you vacuum a cat? Most cats will not volunteer to be vacuumed, though we've met a few who didn't mind. What you get, according to our field and lab tests, if you vacuum a (willing) cat includes: cat hair, cat dander, and typically some pollen, a few dust mite fecals, and common house dust particles.

Animal dander (C) Daniel Friedman

We have found by field and lab testing that cat dander is present (albeit at low levels) even in buildings where no cats live. The allergenic component of cat dander is Feline D-1 or Fel-D1, a glycoprotein that combines with cat dander (cat skin flakes).

When a cat grooms her/himself and when cat saliva (from grooming, and which contains Fel-D1) combines with additional Fel-D1 produced by cats' sebaceous glands. Fel-D1 is also written Fel d-1 and Fel D 1).

But put more simply, a glycoprotein found on cat skin flakes or cat dander, is a bothersome allergen to some people.

These cat dander particles, which is basically cat skin flakes, are often "hooked" or sharply irregular in shape, helping these particles to travel from building to building on people and their possessions, from cat-areas to non-cat areas.

While reducing the level of cat dander in the space to be occupied by the cat-allergic person (your daughter) will be helpful, it's tough to predict how she'll react in the home.

We have encountered individuals who were sensitive to very low levels of specific particles in buildings, including animal dander as well as mold and other allergens.

What to Do About High Levels of Cat Dander, Cat Hair, Cat Allergens in a Building

If we find that there is evidence of a high level of cat dander or other problem allergens in the building dust, we could design a cleaning regimen that can substantially reduce those levels, ranging from discard of materials to HEPA vacuuming to washing certain surfaces. As this can get costly I wouldn't do so unless needed.

We might also suggest some special measures for more ordinary house cleaning such as buying a HEPA-rated house vacuum cleaner, reduction or elimination of wall to wall carpeting, and a regular cleaning schedule.

If there appear to be building related health or allergy complaints after cleaning we can suggest additional measures to reduce the allergen level indoors, and perhaps, (let's hope it's not needed) recommend a more thorough building investigation for other problem sources.

For details on how to remove or clean up cat allergens see CAT DANDER REMOVAL - separate article

Cat dander particle size & particle movement within individual buildings

Indeed there are some particles such as very small mold spores (as small as 1-2 microns) produced by Aspergillus sp. or Penicillium sp. that are so tiny that they can move through a building like a gas, riding thermal air currents (warm air usually rises through buildings), and even passing from areas such as a moldy crawl space or basement up into the living area through very tiny openings, cracks, etc.

But larger, heavier airborne particles such as many pollen grains and animal dander do not move like gases through the building. Cat dander, in particular, is a particle that we find ubiquitous in homes and even in many office buildings, even when cats are not themselves present in the building. In my experience and based on both field and lab examinations of indoor particles from several thousand buildings, it is apparent that these particles are very widespread where both humans and cats are present in a community.

If you examine cat dander under the microscope (red arrow in our photograph just above) you'll see that cat dander particles are comparatively large, in some cases in width about the same as a cat hair, and certainly these particles are 10-50 times larger than the smallest (1-3 micron) mold spores.

You'll also see in our cat dander photograph that cat dander particles are curved or hooked (unlike dog dander). I speculate that the size and shape of these particles mean that they are readily attached to clothing and other objects and thus are readily transported not only from one room in a building to another, but even between buildings.

For example when inspecting and testing the administrative offices of a medical building where IAQ complaints were present, we found significant levels of cat dander on the fabric-covered chair, clothing, and even the desk of one worker who lived in a home with several cats. There were no cats occupying the building where these tests were performed, and the level of cat dander was much less or close to zero at the desks of other workers in the same area.

What these cat dander findings mean, in a practical sense, is that in a home where one or more occupants has a cat allergy, you may reduce the level of cat dander in the allergic-person's bedroom, say, by keeping cats out of the room, but by no means will cat dander be eliminated from that space, since those particles seem to be readily tracked or carried into the room from other areas in the home.

Giving a second example, we inspected and tested the bedroom and other areas in a home where a child had severe cat allergies. The parents did not allow the family cat out of the basement. Yet we found significant levels of cat dander in the rooms on upper floors in the home.

In conclusion, while we have not found that cat dander travels as an airborne or aerobiological particle riding warm air currents as might gases or very small (1-3 micron) mold spores, cat dander does travel widely through a building from areas of a concentrated source, apparently by mechanical means such as becoming attached to clothing or other objects that are moved between building rooms.

Even if you tested your apartment for the presence of cat dander or other allergens the result can't be assured to cause your neighbor to abandon her cats - at least some of whom are sure to be, for her, members of her family.

Besides, even if all of the downstairs neighbor's cats moved out tomorrow, that space would continue to be a reservoir of cat dander unless it were very extensively cleaned. All is not lost, however.

You should be able to improve the comfort level in your own home by reducing the level of irritating particles by minimizing the level of house dust in your own home, and in particular, by regularly using a HEPA-rated vacuum cleaner to dust and clean the surfaces in your space, and perhaps, by limiting visits with your catty neighbor to visits outside your own apartment.

The question of whether or not you can or should ask your neighbor not to have cats in her own home is one that you and she will have to work out between yourselves.

Details about methods to reduce the level of cat dander in buildings are found at this companion article: CAT DANDER CLEANUP, PREVENTION

At ALLERGENS in buildings, RECOGNIZING we discuss and provide photos of common indoor allergenic particles found in homes and in the work place.

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 or URINE ODOR SOURCE DETECTION for suggestions about removal of pet odors.

Off-site resources on controlling pet allergens

Most expert sources agree that " - the most effective method to control exposure to animal allergens is to keep your [building] pet [and animal-pest] free."


Continue reading at CAT DANDER REMOVAL or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



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Articles on Animal IAQ & Hazards at Buildings

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