dust mite (C) Daniel Friedman Allergens in Buildings
How to Identify Common Indoor Allergens and Mold by Visual Inspection, Photos and Description

  • ALLERGENS in BUILDINGS - home - CONTENTS: Photo guide to common allergens in buildings - pictures of & comments about cat dander, dog dander, mold & dust mites in buildings
  • POST a QUESTION or READ FAQs about how to identify common indoor allergens and related particles by transmitted light microscopy.
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Photo guide to common indoor allergens:

This article uses photographs to illustrate and help identify various indoor allergens like mold, cat allergens, dog allergens, mouse or rodent allergens, dust mites, cockroach and other insect fragments, mite fecals, and other help in identification of indoor allergens such as cockroaches, dust mites, fleas, house dust, mold, mildew, pet dander, pollen.

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Photographs of Indoor Allergens and Allergenic Particles

Sources of cat and dog hair (C) Daniel FriedmanArticle Contents

Cat Dander and Cat Hair in buildings

photo of cat hair (C) Daniel Friedman

Cat dander (the black kitten Pippin at above left) is for many people a more serious allergen (and asthma aggravator) than dog dander (the dog katie, above). Our page top photo shows insect jaws collected during a survey for dust containing cockroach parts and allergens.

Cat dander is widespread and we even find it present, usually at lower levels, in offices and homes where no cats reside. Animal dander may be brought in by dust and clothing on visitors. Our second photo (above left) shows cat hair in the microscope.

Details about finding and removing animal dander in buildings are provided at CAT DANDER in BUILDINGS.

Dog Dander and Dog Hair in buildings

Dog stains (C) Daniel Friedman

Animal allergen Photos is our article on inspecting and addressing allergens from cats, dogs, and many other animals.

Pets, Pet Hair and Pet Dander as well as dust mites associated with animal dander are very common allergens in buildings.

The wall stains in this photo (above left) were caused by pets, probably a large dog, indicating that further indoor screening for animal dander may be in order.

Dog allergens photo (C) Daniel Friedman Dog allergens photo (C) Daniel Friedman

Our photos above show dog dander (along with human skin cells) stained pink with acid fuchsin to aid visibility for the photograph). Our photo at right shows dog hair collected in an indoor dust sample, in this case the hair is further identified as from a golden retriever.

Testing people for exposure to allergens is a different activity from testing buildings for the presence of animal or other allergens.

When human tests, such as the ELISA and RAST tests for exposure to allergens, indicate that someone has been exposed to problematic levels of animal allergens, there may still be confusion about just where the exposure is occurring. We discuss testing buildings for presence of allergenic particles such as dog dander, cat dander, insect or roach fragments, etc. at ALLERGEN TESTS for BUILDINGS.

Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner.

For more details see our article DOG, CAT & OTHER ANIMAL DANDER - Information for Asthmatics and Indoor Air Quality

ELISA and RAST tests for Allergen Exposure - The Basics

ELISA "enzyme-linked immunosorbent assay" is a rapid immunochemical test procedure that involves an enzyme (a protein that catalyzes a biochemical reaction) that tests for hormones, bacterial antigens, and antibodies. ELISA testing also involves an antibody or antigen (immunologic molecules).

RAST is an older allergen test (exposure detection) in popular use for testing humans, radioallergosorbent test, an IgE test: In this test, a sample of blood is taken, mixed with the suspected allergen, and the level of immunoglobulin E (IgE) is measured. IgE is an antibody produced by the immune system that indicates an allergic reaction.

The ELISA and RAST allergen exposure tests, their accuracy and their usefulness are discussed

Cockroach Fecals, Fragments, Hairs as Indoor Allergens and Causes of Asthma

Cockroach carapace and hair parts (C) Daniel Friedman


Cockroaches (also see photo at page top) - are the source one of the most common insect allergens found indoors in urban areas.

Cockroach fecal pellets, insect hairs, and insect fragments are often identified in house dust where roaches are present.

Our photo, left, shows cockroach carapace parts and hairs from an indoor dust sample.




Photos and Examples of Dust Mites and Dust Mite Fecals in buildings

Dust mites: our photo (left) shows a dust mite collected in an indoor surface dust sample.

Dust mite photograph (C) Daniel Friedman

We've stained the mite blue using lactophenol cotton blue to make its parts more attractive and easy to discern.

Dust mite fecals (C) Daniel Friedman

Photo of Dust mite fecal pellets & Pen/Asp Mold Spores

Our photo (left) shows a mix of dust mite fecal pellets and Penicillium/Aspergillus spores collected in a surface dust sample from a building.

A close examination of the dust mite fecal pellets (large dark colored particle chain in our photo) can assist in a building investigation for allergens by telling us what the dust mite or other insect was eating

- in this case mold spores.

The small hyaline (colorless) spherical particles are Pen/Asp spores at about 1-5u in diameter.

Photos of Dust Mites

At a much loser magnification than the dust mite fecal photos just above, you can see a dust mite surrounded by other house dust particulate debris.

Photograph of a dust mite surrounded by debris, seen through the microscope

Here is another mite found among pollen in the flower of a Tulip Poplar.

You won't see dust mites without a microscope, but if your home has any or all of dampness, wet areas, pets, lots of dust and organic debris, old mattresses and pillows, couches, carpets, heavy curtains, or if you go to sleep with wet hair on your pillow, you're likely to have a high dust mite population.

Mites, mite parts, and mite fecals show up in indoor dust samples examined by microscope. Dust mites are present wherever people and animals live. But high levels of mite fecals raises the level of allergens in the Building and may be a problem.

Fiberglass Insulation Mold comments about a field study in process, & more about health hazards from fiberglass insulation - DJF

Fleas and Bedbugs as serious building pests also may produce allergens.

Pollen Allergens in Building Air and Dust Samples

Pollen Photo Library a photo library of pollen & the flowers, shrubs, trees from which pollen was collected.

Poppy pollen

Mice and Rats in buildings as Allergen Sources

Mouse hair (C) Daniel Friedman

Mice hair, dander, and fecals are often observed during an indoor air quality or environmental inspection.

Our photo (left) shows mouse hair found in indoor dust during an environmental inspection and test.

We often find mouse droppings, hair, dander, and mouse remains in attics, basements, walls, ducts, and food-storage cabinets.

If mice and rats are a problem in a building, in addition to needing professional extermination services, you'll need to look at the housekeeping practices in the home and in neighboring apartments or homes, especially food storage.

Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings, and high levels of these materials in building insulation in those locations.

If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing rodent problem.

If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some help from a licensed pest control expert.

Mold Allergens and Toxins in buildings

Bathroom mold (C) Daniel Friedman


Mold on laundry room wallWhat mold looks like inside a building

AspergillisMold, a photo library of mold spores for allergy and asthma sufferers - Aspergillus, Penicillium, Stachybotrys, Cladosporium, etc.

Meruliporia incrassata - Serpula lacrymans the "house eating fungus," field and lab photos

How to Find and Test For Mold in buildings - Looking for Mold - A 'how to' photo and text primer on finding and testing for mold in buildings

Recognizing Mold: What mold looks like mold identification photos to help identify mold - choosing what to sample in buildings

Wood & Other Building Dust & Allergens

Reader Question: to avoid wood allergens can I just paint the wood surfaces before insulating the wall cavity?

I have been doing a lot of research regarding the correct way to insulate my home. I have a typical raised ranch where the block wall extends about 4 feet above the slab and in my case it is also above grade.

My question is about the correct way to insulate the 4 feet of stud framed wall that extends above the block. I would like to know if I can paint the plywood with a vapor barrier paint before I insulate to help eliminate any moisture problems and since some members of my family have wood allergies?

Is there any reason why I shouldn’t use the same paint in my attic on the sheathing and rafters? - C.C. New York 11/21/2013


First, you might want to read a bit about the topic starting at VAPOR BARRIERS & CONDENSATION in BUILDINGS But I can add a few specific thoughts:

Even if building occupants have wood allergies, it is not necessary nor appropriate to paint all of the wood framing and sheathing before enclosing a wall.

Proper wall construction will include an air and water barrier on the outside of the wall, insulation in the wall, a vapor barrier on the inside or warm side of the wall (unless you live in a cooling climate such as Florida), and a finish material of drywall or equivalent.

The drywall is then painted or wallpapered or sometimes covered with paneling (which you will eschew as you're avoiding wood and certainly won't be moving to plastic).

That wall construction means that any particles associated with the wood wall structure (which would be minimal anyway in a finished building) will be below the limits of detection.

If your concern is not for particles but for gases or VOCs I'd want to know more, as my research has not found such complaints traced to normal framing lumber.

Ask your doctor, but I suspect she will confirm that the allergy is more specific than that - perhaps to wood dust, to specific wood species, or to mold contamination growing on wood. Pure wood allergies to all forms of wood would be a surprise.

Check With Your Doctor About Allergens

... and About Whether or Not Building Tests for Allergens or Mold are Recommended

Of course since individual sensitivity to allergens varies, we suggest that anyone suffering from allergies and considering steps to further clean their home should also consult with their allergist and their general physician.


Continue reading at ALLERGEN TESTS for BUILDINGS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



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