NEW YORK, Jan 19 (Reuters Health) -- Children who get the measles are just
as likely or even more likely than other children to develop certain types of
allergies, study results suggest.
The new findings contradict a theory known as the "hygiene hypothesis,"
which says that the drop in childhood infections due to vaccinations and better
hygiene is linked to an increase in allergy-related illnesses, such as asthma.
Children who had the measles actually had a 32% higher risk of eczema (red itchy
skin related to allergies), a 41% higher risk of rhinitis (chronically runny
nose due to allergies) and a 67% greater risk of asthma compared with youngsters
who did not get the measles, according to the report published in the January
19th issue of The Journal of the American Medical Association.
The study was conducted by Dr. Mikko Paunio of the University of Helsinki,
Finland, and colleagues. The researchers looked at the computerized medical
records of more than 500,000 children aged 14 months to 19 years, including
nearly 20,700 children who had already been infected with measles at the time
they were vaccinated.
Rather than being less likely to have symptoms of allergic disease, as the
hygiene hypothesis suggests, children with a history of measles infection were
more likely than never-infected children to develop these diseases.
However, the new study does not represent the last word on the hypothesis,
according to an editorial by Dr. James E. Gern, of the University of Wisconsin
Medical School in Madison, and Dr. Scott T. Weiss, of Harvard Medical School in
Boston, Massachusetts.
Exposure to infectious diseases in general -- particularly lower
respiratory tract infections -- may protect against allergic diseases, they
note. Therefore, the results of the new study can be explained by suggesting
"that measles infection is not a good indicator of overall exposure to
infectious disease in a Western environment such as Finland," Gern and Weiss
write.
Other factors, such as the timing of infection, may also be important,
according to the editorialists.
"What is needed are prospective studies to evaluate effects of childhood
infections on development of the immune system, and prospective data on the
effects of viral and bacterial infections on... allergic inflammation," Gern and
Weiss conclude.
Such information could help researchers to better understand the causes of
allergic disease, and may even lead to the discovery of new ways to prevent
these diseases.
