Jan. 22 (iVillage Total Health) -- Scientists have discovered that the chemical responsible for allergic reactions may also play a role during bacterial infections, according to research published this month.

The study, which used mice, suggests that use of antihistamines - the traditional drugs used to fight allergy symptoms - may be effective at reducing swelling, inflammation and other symptoms associated with lung and airway infections. However, additional research is needed to confirm whether the same results can be achieved in humans.

Researchers from the University of California at San Francisco studied two groups of mice -- a normal group with characteristics similar to wild mice and a group with genetic defects that cause them to lack mast cells, the cells traditionally believed to produce inflammation-causing histamines in allergic reactions. Histamines are the chemicals responsible for the nasal congestion, blood vessel constriction and watery eyes common among people with allergies. Both groups of mice were exposed to a common respiratory bacterium and both groups subsequently developed pneumonia.

Scientists expected to see fewer symptoms of inflammation, wheezing, runny noses and eyes in the mice without histamine-producing mast cells. However, these mice actually had worse symptoms than the normal mice. The histamine levels were up to 50 times higher in the mice without mast cells than in the group with them.

That suggested to researchers that histamines were being produced elsewhere in the infected mice. They discovered that neutrophils -- the most common type of white blood cell used to fight infection -- were producing enzymes that produced the histamine. After the sick mice were given antihistamines, the histamine levels dropped and their pneumonia improved.

"This study was in mice so we cannot freely extrapolate the results to human beings," lead investigator George H. Caughey, M.D., said in a press release. "Nonetheless, antihistamines may deserve more of a look as therapeutic options in lung and airway infection."

He noted that the study may have implications for people with airway disorders such as cystic fibrosis , asthma and bronchitis.

The study appeared in the January issue of the Journal of Experimental Medicine.

Copyright 2007 iVillage Total Health.