Early exposure to common viral infection does not protect against allergy

Common viral infections in early childhood do not protect against allergy, concludes research in Thorax. If anything, the evidence points to an increased risk.

The findings contradict the increasingly popular if general theory that the rise in prevalence of allergies and asthma is partly attributable to the fact that children are less frequently exposed to viral infections early in life – the so-called ‘hygiene hypothesis.’

The research focused on 889 pregnant Danish women, who were part of a national birth study. Their medical records were examined to see if they had had measles, rubella, chicken pox (varicella) and mumps before school entry (age 7 in Denmark).

The women’s allergic responsiveness was tested using 11 common allergens, including domestic animals, grass, dust mites, and mould. Two hundred and sixty one were classified as having an allergic (atopic) response to the allergens.

There was no association between atopy and childhood infection with rubella, chicken pox, or mumps, even after adjusting for influential factors, such as number of siblings, year of birth, and social class. And the authors found an increased risk of atopy when measles was acquired during the first year of life.

The greater the number of infections acquired before the age of 2 years, the greater was the risk of subsequent atopy.

The authors conclude that childhood infection with measles, rubella, chicken pox or mumps, even if acquired very early in life, does not protect against atopy.