by CIGNA HealthCare Allergy
Contact with animals has long been recognized as a source of allergic reactions which may affect the eyes, nose, lungs, or skin.
The allergen source varies with the animal but is generally considered to be water-soluble protein material that can be absorbed from the mucosa by inhalation or from the skin by contact. Extracts for testing reactions to animals have been obtained by washing or pelt extraction and by use of the serum or urine of the animal. The allergens identified are lighter than the house dust mite allergen and therefore are easily airborne.
Any mammal may become a significant source of indoor allergens in the home. As cats have been known to be highly allergenic, the cat allergen is one of the best studied and characterized. The source was first felt to be the cat dander and then the saliva on the cat’s coat. It is now felt to be a secretion of the cat’s skin and fur, also present in the urine of male cats. This material has been identified and named Fel d 1. It is an internationally standardized extract than can be measured and used for treatment in certain situations, such as obligatory occupational exposures (e.g., veterinarians). Fel d 1 is found in high concentrations in households with pet cats and is concentrated in cat bedding, carpets, and upholstered materials and mattresses. It is also a problem in litter boxes, particularly of male cats. Fel d 1 may be found in lesser concentrations in homes without cats and may be carried on the clothing of individuals entering that home.
Dogs have also become indoor residents of American homes, and the source of the major allergen seems to be the dander of dogs. Dander is defined by Webster as minute scales from hair, feathers, or skin, that may be allergenic. The hair per se is not a water-soluble material and therefore not the source of the problem, but the allergen may be attached to portions of the hair. There are no non-allergenic dogs. The principle dog allergen has been isolated and named Can f 1. This major allergen has been identified as a source of the respiratory reactions that people have upon exposure, including rhinitis and wheezing. Contact reactions are reported as well, particularly localized hives due to licking and a presumed sensitivity to salivary protein. Can f 1 can now be identified accurately but the amount of material airborne in a household has not been reported. As it is a lighter weight material than Fel d 1, it would be reasonable to assume significant respirable material is available in the household air.
Wild and pet rodents (such as mice, rats, gerbils, hamsters, and guinea pigs) have the major allergen identified in their urine, particularly as it dries and becomes airborne. Their bedding and litter and any dried material on the animal then come potent sources of allergenic material for the susceptible patient.
Birds may result in allergic reactions via exposures to material derived from their feathers. Bird fanciers may also be afflicted with a type of pneumonia called hypersensitivity pneumonitis.
Large animals (horses, cows, donkeys) maintained in fields and barns have potent allergens generally attributed to their dander. A patient with a horse dander allergy will also react to donkeys in a similar fashion. However, many difficulties are encountered in studying the source of barn-related sensitivities due to the presence of significant fungi, mites, and rodent allergens.
The first principle for allergy control is avoidance, and this basically involves getting the source of the allergen out of the living environment. For an indoor pet, the ideal is to get it out of the household, but definitely out of sleeping quarters. It does no good to buy an expensive air purifier to circulate the room air through special filters if a large source of allergen is still present. Studies have suggested that frequent bathing of cats along with removal of carpeting and porous materials of furniture, drapes, and bedding, plus the use of a room purifier with HEPA filters, may help control the allergen load. If the cat is removed and no other measures are taken, the measurements of Fel d 1 in the environment are still extraordinarily high weeks to months later—leading to the complaint, “It wasn’t the cat, I’m no better since he has been outdoors.”
Note: Highly allergic people may develop an allergy to an animals once it is introduced into the environment, so past negative testing to an animal does not preclude future or ongoing sensitization and allergic disease.
Posted in: Animals