The indoor air and asthma: the role of cat allergens

Curr Opin Pulm Med. 2012 Jan;18(1):29-34. doi: 10.1097/MCP.0b013e32834db10d.


Purpose of review: The objective is to discuss recent progress in our understanding of the role of the indoor environment in asthma, focusing on the special role of cat allergens.

Recent findings: Sensitization to Fel d 1 is the dominant event in inhalant responses to cat; however, there are also IgE responses to the lipocalin (Fel d 4), to cat albumin (Fel d 2), and to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal) on cat IgA (Fel d 5w) and other molecules. The dose response and routes of sensitization for these allergens are now thought to be diverse. It is important to remember that exposure outside a house with a cat is sufficient to cause sensitization. Furthermore, the only solid evidence about a role in asthma relates to Fel d 1. Recently, it has been shown that tolerance associated with early exposure to cats can persist to age 18 and that IgE to alpha-gal (on cat IgA) is not related to asthma. In addition, a recent study of anti-IgE reinforces the evidence that IgE antibodies to indoor allergens make a major contribution to asthma severity.

Summary: Exposure to Fel d 1 in a home with a cat is far higher than the levels necessary to induce an allergic (IgE antibody) response. In keeping with that, children may develop tolerance, which can be long-lived. In addition, there is increasing evidence that IgE antibodies to an inhalant allergen, such as Fel d 1, dust mite, or cockroach, are causally related to lung inflammation and asthma.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Air Pollution, Indoor
  • Allergens
  • Animals
  • Antigens, Plant / immunology
  • Asthma / epidemiology
  • Asthma / etiology
  • Asthma / immunology*
  • Cats
  • Cockroaches / immunology
  • Dust / immunology
  • Environmental Exposure
  • Glycoproteins / immunology*
  • Housing
  • Humans
  • Hypersensitivity / etiology*
  • Hypersensitivity / immunology
  • Immunoglobulin E / immunology*
  • Lipocalins
  • Mites / immunology
  • Serum Albumin / immunology


  • Allergens
  • Antigens, Plant
  • Dust
  • Fel d 2 allergen, Felis domesticus
  • Fel d 4 allergen, Felis domesticus
  • Glycoproteins
  • Lipocalins
  • Serum Albumin
  • Immunoglobulin E
  • Fel d 1 protein, Felis domesticus