ALLERGENS IN THE INDOOR ENVIRONMENT
FACT SHEET

Definition:  
A broad array of pollens, fungi, algae, actinomycetes, arthropod fragments, dusts, and pumices 
have been confirmed as airborne antigen sources that evoke human responses; evidence similarly 
implicating airborne bacteria, protozoa, and other groups is still emerging.

Characteristics:  
Allergic reactions can occur on the skin and in the nose, airways, and alveoli.  Although 
increasingly recognized as important causes of allergic lung diseases, occupational agents are considerably 
less prevalent as causes of these diseases than such allergens as pollen, molds, mites, and animal dander 
and excreta, to which exposure occurs in the home environment.

Sources: 
Pollen is ascribed to sources:  nature, whose presence in the indoor environment reflects incursions 
from outdoor air. E.g., pollen from grass, trees, flowers are most abundant in the summer months (1).
House dust mite:  usually associated with mattresses, bed clothes, and heavily used upholstered 
furniture (2,3).  E.g., dermatophagoides pteronyssinus and D. favinae species are abundant indoors (3,4); 
also, Glycphagus, Hirstia, Tyrophagus, and Euvoglyphus inhabit dust.  Temperature of 25oC and humidity 
of at least 45% favor growth of mites, especially during autumn.

Moulds/Fungus:  cases of contamination of domestic interiors usually involve outdoor fungi that 
increase indoors on specific substrates.  Clorisporium is the most frequent toxin recovered both indoors and 
outdoors, especially on damp walls (5). Pencillium concentrations increase with house cleaning and repair 
and are found in damp cotton, leather, and paper.  Aspergillus is a common indoor fungi (6,7) found 
particularly in damp cotton, paper, and leather.  Aspergillus fumigatus is a ubiquitous soil fungus and can 
be found wherever organic material provides a substrate.  House plants have been implicated as sources of 
increased concentrations in homes and hospitals.  Poor landscaping practices, including accumulation of 
organic debris and high shade, and applicances such as evaporative humidifiers and air conditioners are 
potential sources of air-borne fungal contamination (5,8).  Algal particles are regular components of 
outdoor aerosol and are regarded as potential human allergens (9).

Animal dander and excreta of domestic animals:  Dogs, rabbits, guinea pigs, and horses and 
particularly cat dander are sources of allergens.  Animal urine is an important source of allergenic protein 
(1).  Feces of birds, particularly of parakeets and pigeons, can stimulate IgE antibody production (10). 
Feathers, present largely in bedding and clothing, are sensitizers that acquire antigenic potency with age 
(11).  Fragments of epidermis and skin appendages (danders) are shed by all vertebrates and dispersed 
indoors.  With components of sweat, saliva, and waste discharges, these particles may contribute 
substantial quantities of species-specific materials to the indoor environment (1).  Insects:  Emanations are 
strong sensitizers.  Indoor species include:  roaches, house flies, bedbugs, and carpet beetles (1).

Concentrations:
House dust may contain 10,000-3,000,000 spores/m3.  Dust-raising activities increase spore counts in 
domestic interiors (12).    Repair work may increase counts up to 20-fold probably due to dust dispersion.
Merulius laerymans, contaminating damp timbers in old homes, may produce potentially sensitizing spores 
indoors at up to 360,000/m3 (14).   A. fumigatus counts are generally low:  0-200/m3 however, interiors in 
which organic material is stored or handled can exceed 2 x 1010 spores /m3 (16).  In the presence of 
compost, counts can rise to the millions per cubic meter (17).

Standards:  There are currently no standards for air allergens.

Health Effects:
Both primary irritants and allergic sensitizers may produce inflammation of the skin or an 
eczematous process.  Primary irritation causes contact dermatitis.  Secondary effects may occur after 
cutaneous defenses have been removed.  Bacteria may grow in oozing fissured skin. Allergic responses to inhaled materials cause a local inflammatory reaction that affects predominantly the nose (allergic rhinitis), the airways (allergic asthma), the airways and adjacent alveolar spaces (allergic asthma with pulmonary eosinophilia--allergic bronchopulmonary aspergillosis), or alveoli and peripheral bronchioles (hypersensitivity pneumonitis or extrinsic allergic bronchioloalveolitis).

Allergens Bibliography:

National Institutes of Allergy and Infectious Diseases.  "Pollen allergy".  U.S. Dept. of HHS, PHS, NIH. 
Washington, D.C. 1980.

National Institutes of Allergy and Infectious Diseases.  "Allergies: questions and answers".  NIH.  
Washington, D.C.  August 1984.

Kelsey, Patricia A.  "Car a/c mold heightens allergies in 18% of patients in LSU study".  Air Conditioning, 
Heating, Refrigeration News v163 Sept 3 '84 p10(1).

Strachta, Bruce J.  "Are you allergic to your job".  Safety & Health v135 June '87 p40(4).

Nickel, Jeffrey.  "Allergies".  Safety & Health v140 Sept '89 p50(4).

Silberner, Joanne.  "How to turn your home into a sneeze free zone: household allergies".  U.S. News and 
World Report v106 Feb 20 '89 p70(2).

"Two faced side of cosmetics(allergic reactions caused by ingredients of cosmetics)".  Changing Times v39 
March '85 p12(1).

Silberner, Joanne.  "Allergy Warfare".  U.S. News and World Report v100 Feb 20 '89 p68(7).

Hochman, Gloria.  "Allergic to everything: when you react to the very fabric of life, that spells trouble".  
Health March '86 p53(6).

"Facts about allergies and the immune system".  Consumer Guide Magazine v440 March '87 p31(11).

Yulsman, Tom.  "Allergies; a new front is being opened in the war against hay fever and asthma".  The 
New York Times Magazine April 17 '88 pS10 col 1.

"Fighting hay fever".  Consumers' Research Magazine v72 May '89 p30(4).

Chandler, Michael J.  "We are beginning to unlock the mysteries of allergies(advertising supplement)".  
Newsweek v113 May 22 '89 p54(1).