Regular physical activity might offer children some protection from the sniffs and sneezes of hay fever, a study suggests.

German researchers found that among the 1,700 children they followed for up to 12 years, those who were inactive at the study's start were 50 percent more likely to develop hay fever, compared with their regularly active peers.

According to the researchers, their findings are unlikely to be a case of "reverse causality," where hay fever caused some children to avoid outdoor activities. For one, the study followed the children over time, documenting new cases of hay fever. In addition, sedentary children were inactive year-round, not only during pollen season.

Instead, the findings, published in the journal Allergy, suggest that regular exercise may somehow keep hay fever at bay.

Exactly how is unclear, said Dr. Yvonne Kohlhammer, the study's lead author and a researcher at GSF - National Research Center for Environment and Health in Neuherberg, Germany.

Other studies, she stated, have shown that moderate exercise may benefit immune system function. So this might explain the lower hay fever risk seen in active children, Kohlhammer speculated.

The study included 1,703 children ages 5 to 14 who were first examined in 1992-1993, then at least once more over the next 12 years. During the first assessment, parents reported on their children's physical activity levels; only 6 percent were completely sedentary, while 79 percent regularly exercised or played sports.

Sedentary children, the study found, had more than twice the rate of hay fever as regularly active kids, and their risk of developing the allergy during the study period was also elevated.

The link between exercise habits and hay fever persisted even when the researchers weighed other factors that affect children's allergy risk -- including family history of allergies, exposure to pets and cigarette smoke, and whether a child was breastfed or bottle-fed.

If the findings are correct, hay fever protection could be one more reason for kids to be regularly active, according to Kohlhammer -- though for now, she noted, that remains speculation.

SOURCE: Allergy, November 2006.