Facebook posts claim pneumonia caused by Covid-19 is an allergic reaction that should be treated with antihistamines. But experts dismissed the claim, saying pneumonia associated with the disease is not related to allergies, and that antihistamines have not been proven to be beneficial in treating Covid-19.
"C o V I D pneumonia is actually mast cell degranulation of the lungs!! Put simply, it's an allergic reaction occurring after the viral phase ends, most likely to something in the viral particles left over after the body deals with the virus," says a January 14, 2022 Facebook post, calling it "the great misdiagnosis."
The post attributes the information to a South African doctor, and urges readers to "add antihistamines to your C protocol!"
More examples of the claim -- one of many inaccurate assertions spreading online about Covid-19 -- appeared on Facebook here, here, here and here.
Peter Chin-Hong, an infectious disease physician at the University of California, San Francisco said the claim is "completely false. There's no basis to it."
"It's not an allergic reaction," he said, and there have not been large, randomized clinical trials that have shown antihistamines to be beneficial against Covid-19.
Chin-Hong discouraged people from taking antihistamines to treat Covid-19 at home, possibly delaying a hospital visit. "It's dangerous when people think they can treat it, because time is money with disease," he said.
The sooner patients come in to get medical attention, the better doctors are able to treat you for severe illness, he explained.
He also cautioned against anecdotal reports of successful treatments, saying until scientific findings can be reproduced and peer reviewed, "you can't really always believe that this is correct or accurate."
Panagis Galiatsatos, a pulmonary and critical care medicine physician at Johns Hopkins Bayview Medical Center, said allergic reactions and infection responses represent different lines of defense for the body.
Thorough profiling on Covid-19 has consistently shown that the body produces an infectious immunological response -- not an allergic reaction -- when confronting the disease, he said, calling the social media claims "preposterous."
Mast cell degranulation, claimed by the posts to be the cause of Covid-19 pneumonia symptoms, is not involved, Galiatsatos said.
Mast cells act on pollutants to get them out of the body and are responsible for symptoms caused by seasonal allergies. The inflammatory markers typical of Covid-19 are not released by mast cells.
"The pneumonia happens because of the aberrant immune response," he said. "We have this cascade of the immune system that just can't be well controlled. Literally what ends up happening in Covid pneumonia, severe Covid, is like a bull in a china shop. The bull is destroying the virus, and your organs at the same time."
Joshua Solomon, a pulmonary disease specialist at National Jewish Health in Denver, Colorado, called the social media posts "unequivocally false," adding that "histamine and mast cells really have nothing to do with it."
"The thought of antihistamines saving people (from Covid-19) is just not based in reality," he said.
The US Centers for Disease Control and Prevention offer guidelines on what to do if you become sick with Covid-19 here.