Early Fevers May Protect Kids From Allergies

Study Lends Support to 'Hygiene Hypothesis'

WebMD Health News

Feb. 9, 2004 -- Infants who suffer a fever before their first birthday have a lower risk of developing allergies by age 6 or 7, a new study shows.

Researchers say the findings provide support for the hygiene hypothesis, which holds that early exposure to infections help strengthen young immune systems and protect children against allergic diseases later in life.

"The hygiene hypothesis is widely recognized but largely unproven," says Kenneth Adams, PhD, who oversees asthma research funded by the National Institute of Allergy and Infectious Diseases (NIAID), which helped fund the study, in a news release. "The findings of this study strengthen the hypothesis and, after more research, could lead to preventative therapies for asthma and allergies."

Researchers say that the prevalence of allergies and asthma among children has increased dramatically in recent years, and this study provides evidence that reduced exposure to potential infections may be one of the reasons for this trend.

The results of study appear in the February issue of the Journal of Allergy and Clinical Immunology.

Early Infections Protect Children Against Allergies

In the study, researchers followed a group of 441 children from birth to age 6 to 7 years to see if fever -- as an indication of exposure to infection -- before age 1 was linked to developing allergies or asthma later in life.

Of the 441 children, nearly half (47%) developed a fever by age 1, and a total of 321 episodes of fever were reported, such as ear infections and upper and lower respiratory tract infections. Fevers were defined as a rectal temperature of 101 degrees Fahrenheit or above.

When the children were examined from age 6 to 7, researchers found that 50% of children who did not experience a fever during their first year of life had become sensitive to common allergens such as dust mites, ragweed, and cats. Children who had one fever were slightly less prone to allergies with 46.7% developing these allergic sensitivities by age 6 through 7.

But the study showed children who suffered two or more fevers during infancy had greater protection. Only 31.3% of children in this group developed allergies by ages 6 through 7.

"We didn't expect fever to relate with such a consistent effect," says researcher Christine C. Johnson, PhD, MPH, of Henry Ford Health System in Detroit, in a news release. "It was also interesting that the more fevers an infant had, the less likely it was that he or she would be sensitive to allergies."

Researchers say that although these findings provide direct support for the hygiene hypothesis, more information is needed to determine the types of infections that protect against allergies and how they work.

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