CAT

The Two Studies

Risk of eczema in the first year of life was at least double in children who had a cat in the house and bearing the mutation; the mutation consists of a filagrin protein deficiency , say Hans Bisgaard of Gentofte University Hospital and his colleagues.
Children exposure to dogs or house dust mites had no effect on the risk of developing eczema, two studies have shown. To reduce the risk of eczema, children with this mutation should not be exposed to cats in the first few months of life.
Filagrina is part of Keratohialine, which can be found in the stratum granulosum of the epidermis and helps reduce water loss and provides protection from the environment. Dr. Bisgaard’s group previously showed that functional gene variants that cause filagrine occurance are the main causes resulting in eczema.
To see if early exposure to allergens is added to the genetic risk, researchers examined two groups, first, in Copenhagen, including 379 infants with an increased risk and the second group, comprising 503 children from Manchester Asthma and Allergy Study.
In both studies, mutations of the filagrine were for the experts the most important influences on the risk of eczema in early ages. In the high risk group, 28% of the children were diagnosed with eczema before the first year (equivalent to 105 children). Among 40 children with serious mutations of filagrine from the Copenhagen group, 18% had a dog in the house at their birth, 11% had a cat and 3% a dog and a cat .
The presence of the cats seems to have been the only factor that increased the risk of allergen eczema, but only in children with mutations in filagrine. The presence of the dogs was associated with a reduction in the occurrence of eczema, but without an interaction with the genotype of filagrine.
In the Manchester group, 37% of the 503 children developed eczema at the age of one year. And here, a small number of children had filagrine mutations (10%, 50 total). They had the same probability of having pets at home as other children. (17% versus 22% had a dog, 13.2% versus 12% had a cat and 5.1% versus 4% had both animals)
The Manchester group confirmed an increased risk of developing eczema by the age of one year, with filagrine mutations, although the increased risk of these children, with a cat in their house, was not so high as in the group in Copenhagen. In this study, one dog in the house showed that tends to have a protective role, but not significantly. No study has demonstrated a significant interaction with house dust mites.
The effect seems to be independent of allergic sensitization, the mechanism is unknown, researchers say. Other possibilities are the pyrogens, such as the colonization of bacteria that enter the respiratory route, or that exposure to cats may be a surrogate marker for other unknown influences of environment which penetrate the skin barrier due to imperfect synthesis of profilagrine.