New research suggests estrogen could be the factor behind why women suffer more severe allergic reactions than men.

A research team found estradiol, a type of estrogen, enhances the activity of an allergic reaction-driving enzyme present in mice, the National Institute of Health (NIH) reported. The findings provide insight into why women tend to have worse allergic reactions than their male counterparts. The findings also highlight the importance in accounting for gender differences in animal experiments.

In anaphylaxis allergic reactions, immune cells release an enzyme that causes tissue to swell; this can cause skin rashes or even breathing difficulties and heart attack. Past studies have found women are more likely to experience anaphylaxis in response to triggers such as medication, insect bites, or foods than men.

In the recent study researchers found female mice experience "more severe and longer lasting" anaphylactic reactions than males.

The study's results suggest estrogen influences blood vessels by enhancing levels of endothelial nitric oxide synthase (eNOS), which is responsible for some of the symptoms of anaphylactic reactions. The researchers found that when eNOS was blocked, the gender disparity in severity of reaction was greatly reduced, or disappeared altogether. Giving the mice estrogen-blocking treatments also proved to reduce the level of allergic reactions to about what was seen in their male peers.

"While the study has identified a clear role for estrogen and eNOS in driving severe anaphylactic reactions in female mice, more work is needed to see if the effects are similar in people and may be applied toward future preventive therapies," the researchers stated.

The findings were made by researchers from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), and were published in  a recent edition of the Journal of Allergy and Clinical Immunology.