It is common for families prone to allergic diseases to be advised against keeping pets, but new data suggest it may be time to stop blaming the family dog or cat for the allergic reactions.

Instead, say Scandinavian researchers, exposure to pets early in life appears to reduce the risk of developing atopic conditions, including asthma and allergic rhinitis.

To investigate the affect of pets on atopy, the researchers examined data from 2531 children, followed from birth to age four years. When these children were born, 22.4 per cent of the homes had pets. Dogs were kept in 9.1 per cent of homes and cats in 7.1 per cent.

Pet exposure was associated with a small increase in risk of bronchial obstruction during the first two years of life, but the risk for atopic eczema, asthma and allergic rhinitis was actually less in the households with pets.

These findings, the researchers conclude, may have several explanations, among them the possibility that early exposure to pets has a protective effect or that keeping pets is associated with a lifestyle that protects against the development of atopic diseases (Allergy, 2001; 56: 307-12).

Another report adds fuel to the hygiene hypothesis that early exposure to microbes can protect against atopy. Finnish scientists randomly administered either beneficial bacteria (Lactoba-cillus GG) or placebo to pregnant women who had a partner or close relative with eczema. Their infants were then given the same treatment for six months. The incidence of eczema in the treated group was half that of the placebo group (Lancet, 2001; 357: 1076-9).