Anaphylaxis can happen to anyone when an allergic reaction is severe enough to cause life-threatening symptoms, but it appears women experience severe allergic reactions more than men. According to a study, estrogen is the culprit.
Anaphylaxis is tricky to study because of its life-threatening nature. It accounts for around 200 deaths in the United States every year, and numbers could be bigger because it is not known just how many die from unrecognized anaphylaxis. For example, an old man suffering from heart disease may die after succumbing to a heart attack but the heart attack could've been triggered by a very severe allergic reaction.
In a study published in The Journal of Allergy and Clinical Immunology, researchers from the National Institute of Allergy and Infectious Diseases found that female mice are likelier to experience more severe anaphylactic reactions than their male counterparts. They also discovered that instead of targeting immune system cells, estradiol, an estrogen, enhances the activity and level of endothelial nitric oxide synthase (eNOS) which produces some of the symptoms associated with anaphylaxis.
With just plain eNOS in their system, a person undergoing anaphylaxis will experience a drop in their blood pressure which will then let blood vessel fluid leak into tissues to result in swelling. Strengthen the enzyme with estradiol and these symptoms will grow more severe.
To determine if estradiol is the culprit, the resulting activity caused by the estrogen enhancing the enzyme was blocked in female mice. When an allergen was introduced, the female mice experienced allergic reactions at levels and lengths the same as males, taking away gender as a factor.
"More women than men are admitted to hospitals for anaphylaxis, and that tells you something is going on here. Too often these gender differences are not focused on. We need to be better at associating diseases with gender," said Dean Metcalfe, M.D., NIAID Laboratory of Allergic Diseases chief and a co-author for the study.
Researchers want to further study the effects of blocking estradiol in people but claim the results of this study should help in raising awareness in certain sets of individuals, like women of child-bearing age, women taking L-arginine supplements, women on hormone replacement treatment and healthcare providers.
The study received support from the Research Foundation Flanders, the NIAID's Division of Intramural Research Program and the Gustave Boel-Sofina-Belgian American Educational Foundation. Other authors include: Ana Olivera, Ph.D., Alasdair Gilfillan, Ph.D., Geethani Bandara, Ph.D., Avanti Desai, MSc. and Valerie Hox, M.D., Ph.D.
