Sex hormones leave women at greater risk from deadly allergic reactions

SHAFAQNA- Women are at greater risk from deadly allergic reactions because of female hormones, a new study has warned.

Oestrogens, the primary female sex hormones, worsen allergic reactions and could explain why men are less likely to be admitted to hospital with severe problems.

The study by the National Institute of Allergy and Infectious Diseases, in the US, found oestradiol, a type of oestrogen, enhances the levels and activity of chemical which that drives life-threatening allergic reactions.

When people suffer anaphylaxis – an allergic reaction triggered by food, medication or insect stings and bites – immune cells release enzymes which cause tissues to swell and blood vessels to widen.

Although allergies usually only cause flushing or a skin rash, in extreme cases the swelling can be so bad that it leads to breathing difficulties, shock or heart attack.

Previous clinical studies found women tend to experience anaphylaxis more frequently than men, but why this difference exists has been unclear.

Around 21 million adults in the UK suffer from at least one allergy with 10 million suffering multiple problems.

UK hospital admissions for food allergies have increased by five fold since 1990 with the insect stings, nuts, milk and seafood being the most common culprits. It is estimated that around 20-30 deaths due to anaphylaxis occur in the UK each year.

The study published in The Journal of Allergy and Clinical Immunology found female mice experience more severe and longer lasting anaphylactic reactions than males.

Instead of targeting immune cells, oestrogen influences blood vessels, enhancing the levels and activity of endothelial nitric oxide synthase (eNOS), an enzyme that causes some of the symptoms of anaphylaxis.

When the researchers blocked eNOS activity, the gender differences disappeared. In addition, giving oestrogen-blocking treatments to female mice reduced the severity of their allergic responses to a level similar to those seen in males.

Researchers said more work is needed to see if the effects are similar in people and may be applied toward future drugs to prevent women suffering potentially fatal attacks.

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