Can antihistamines be used to treat Long Covid?

February 17, 2022

Although we don’t yet have a drug treatment for either Long Covid or ME/CFS, one of the more interesting drugs under investigation for Long Covid are antihistamines

As this review article shows, there is a scientific basis to explain how antihistamines might work in Long Covid – as well as some clinician evidence to show that they are helping some people with Long Covid.


“The nice thing about the antihistamines is there's very little downside,” as the medicines are safe, cheap and cause few side effects, Dr. Paul Glynne, the medical director of The Physician's Clinic in London, a consultant physician at University College London Hospitals, and first author of the Journal of Investigative Medicine (JIM) report. For most long COVID patients, “I can't see a good reason not to start antihistamines,” he said.

(That said, the long-term use of some antihistamines has been linked to an increased risk of dementia, particularly in older people, according to The New York Times.)

After publishing their JIM report, Glynne and his colleagues began offering all their long COVID patients antihistamines and have now treated upwards of 200 additional patients using a standard protocol, Glynne said. The patients take a combination of H1 blockers and H2 blockers; in general, H1 blockers are prescribed for inflammation and other allergy symptoms, and H2 blockers are prescribed to reduce the amount of acid produced by stomach cells.

Roughly 65% to 70% of their long COVID patients respond well to the treatment and tend to see improvement in specific symptoms first, namely, their skin rashes and gastrointestinal issues, Glynne said. Other symptoms, such as brain fog and fatigue, generally take longer to improve, on the order of weeks.

Dr Shepherd comments

One of the explanations as to how antihistamines might act in Long Covid involves the way in which there appears to be an overlap between Mast Cell Activation Syndrome (MCAS) and Long Covid

And it’s interesting to note that some people with ME/CFS also have MCAS and benefit from the use of of this type of combination of antihistamines

This is not a recommendation to start using antihistamines to treat ME/CFS

But it is a form of treatment that deserves further investigation

Dr Charles Shepherd,
Trustee and
Hon. Medical Adviser
to the ME Association.
Member of the 2018-2021 NICE Guideline Committee.
Member of the 2002 Independent Working Group on ME/CFS.

Dr Charles Shepherd
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