Individuals allergic to cats develop symptoms very rapidly upon entering a house with a cat, suggesting that the allergen is constantly airborne. This hypothesis was in fact confirmed by air sampling measurements. The most important cat allergen is Fel d 1 which is found throughout all breeds of cats.
Furthermore, scientific studies have pinpointed the exact quantity of Fel d 1 allergen that can produce a 20 percent decrease in forced expiratory volume at one second in cat-sensitive patients. Hence, the implementation of both basic control measures and highly specific immunological approaches is of uttermost importance when addressing this problem.
Basic Control Measures
Several cat allergen avoidance measures can be instituted in the home of a person allergic to cats. Although it is often the least acceptable solution, the animal can simply be removed from the home. After that, a period of approximately 20 weeks is needed for the levels of Fel d 1 in settled dust to fall to that found in homes without any cats.
When removing the animal is not an option, the cat can be confined to certain restricted areas (and should definitely be kept out of the bedroom). Washing the animal can also prove beneficial. As steam cleaning the carpets has no additional benefit over regular vacuuming, more aggressive measures (including carpet removal) can aid in rapid reduction of cat allergen content in settled dust.
In an uncarpeted room, a combination of air filtration with high-efficiency room air cleaner, vacuum cleaning and cat washing was shown to reduce the exposure to cat allergens by 90 percent or more. Nevertheless, the exact effect of such combined measures on the alleviation of allergic symptoms has not yet been fully evaluated.
Specific Immunological Approaches
Allergen-specific immunotherapy (also commonly known as allergy vaccination) has proven efficacious in treating respiratory cat allergies and thus far represents the only approach that is able to modify the natural course of this type of allergy. As conventional allergen-specific immunotherapy is time-consuming and carries a risk of adverse reactions (such as cross-linking of receptors and the release of potent anaphylactogenic mediators), recombinant DNA technology is employed nowadays in order to improve the efficacy and minimize any adverse effects.
Specifically designed Fel d 1 hypoallergens show adequate T-cell-stimulating capacity as well as reduced IgE reactivity and thus are likely-looking candidates for use in allergen-specific immunotherapy for cat allergies. Nevertheless, further evaluation of their effect is warranted in both animal and patient studies.
An alternative approach that directly targets allergen-specific T cells and avoids interaction with IgE is the usage of T-cell epitope-containing allergen-derived peptides, which represents a cornerstone of peptide-based immunotherapy. By using this principle that was applied very early on Fel d 1, antigen-specific tolerance can be successfully induced and symptoms after allergen challenge can be reduced.
Engineered Fel d 1 proteins that have immunomodulatory function often target the inhibitory receptors on basophils and mast cells. Moreover, coupling allergens with particles optimized for phagocytosis represents an encouraging concept for the improvement of allergen-specific immunotherapy protocols.
Reviewed by Susha Cheriyedath, MSc
- Pope AM, Patterson R, Burge H, editors. Indoor Allergens – Assessing and Controlling Adverse Health Effects. National Academy of Sciences, National Academy Press, 1993; pp. 86-130.
- Brooks GD, Bush RK. Allergens and Other Factors Important in Atopic Disease. In: Grammer LC, Greenberger PA, editors. Patterson's Allergic Diseases, Seventh Edition. Lippincott Williams & Wilkins, 2012; pp. 73-103.