University of Cincinnati epidemiologists say that environmental tobacco smoke drastically increases an infant's risk for developing allergic rhinitis (hay fever) by the tender age of 1.

Epidemiologist Jocelyn Biagini says, ‘We found that infants who were exposed to 20 or more cigarettes a day were three times more likely to develop allergic rhinitis by their first birthday than those who were not exposed.’

The study also suggests that infants with older siblings are less likely to develop hay fever. Dr. James Lockey explains: ‘Research has shown that exposure to certain infections early in life may decrease your risk for allergic diseases. We found a 'sibling protective effect' for allergic rhinitis — this may mean the more siblings infants have, the more infections they are exposed to. As a result, the infant's body may be better equipped to fight off allergic diseases later in life.’