Estrogen Found to Increase Severity of Allergic Reactions

in Food Allergy
Published: January 7, 2015
Photo: Getty

A new study is shedding light on why women often have it worse when it comes to anaphylaxis.

It has long been observed that women experience allergic reactions that are more severe compared to men, but clinicians did not understand why – until now. Research recently published in the Journal of Allergy and Clinical Immunology pinpoints estrogen as the culprit.

The study, conducted by researchers from the National Institute of Allergy and Infectious Diseases, used mice to investigate the biology behind the difference between the sexes. Researchers noted that female mice had more severe, longer-lasting anaphylactic reactions compared to their male counterparts – similar to trends observed in humans – however, by reducing the estrogen levels in female mice, this gender disparity disappeared.

“We showed that when you take out the ovaries – you ovariectomize the mice – then there is no difference between the reactions of ovariectomized mice and males,” explains study co-author Dr. Ana Olivera. However, when Olivera and her colleagues injected the ovary-less female mice with estradiol, a type of estrogen, they observed much bigger anaphylactic reactions, indicating “that estrogen is a player in the severity of the response.”

Dr. Ana Olivera | NIAID

Upon closer examination, researchers discovered that estrogen increases the activity of the enzyme – endothelial nitric oxide synthase (eNOS) – that causes tissues to swell and blood vessels to widen, resulting in anaphylactic symptoms such as rashes, breathing issues, and in severe cases cardiac arrest.

So what does all of this mean for women with food allergies?

“It provides a rationale for doctors to perhaps use other treatments in cases of very strong anaphylactic reactions, particularly in women,” says Olivera. According to the NIAID scientist, these treatments could include using medication to inhibit the eNOS enzyme in women who suffer from severe anaphylaxis or simply advising women to take extra precautions at times when their estrogen levels are high, such as right before menstruation or during puberty.

Olivera says with these findings she hopes to make people, particularly women, more aware of the factors involved in their reactions and help improve clinical management.

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