Getting a 'COVID arm' rash after the Moderna vaccine might be itchy, but it's no big deal

• Some people may experience a rash on their injection arm after getting the Moderna COVID-19 vaccine.
• The rash is likely a delayed allergic reaction or hypersensitivity.
• Experts say there's no need to panic, and the rash is not a reason to avoid getting your COVID-19 shots.

Some recipients of the Moderna COVID-19 vaccine have reported a red, welted rash that showed up days after they got their shots.

This delayed skin reaction occurred in less than 1% of phase 3 clinical trial participants, according to a letter to the editor published in the New England Journal of Medicine this week.

Amelia Brown got her first Moderna shot in California on January 11, and her injection arm felt itchy a week later, she told Insider. The morning after the itchiness started, her upper arm was red, swollen, and hot to the touch.

Such a rash is harmless, causing itchiness or aching at worst, and typically goes away within 24 hours to a week, Esther Freeman, director of global health dermatology at Massachusetts General Hospital, told USA Today.

Freeman heads a global database of skin-related COVID-19 symptoms and vaccine reactions. She told USA Today that only 14 people had reported so-called "COVID arm" as of January 27, although more instances likely haven't been reported.

"We want to reassure people that this is a known phenomenon," Freeman told USA Today. "Having a big red splotch on your arm for a couple of days may not be fun, but the reality is there's no need to panic and no reason not to get your second shot."

Brown's rash subsided after a few days and was gone by the end of the week. She got her second shot a month later after checking with her doctor.

'COVID arm' is likely a minor allergic reaction

Toronto physician Iris Gorfinkel told CTV News that "COVID arm" is likely a delayed allergic reaction. The redness is a predictable reaction to any shot, and it's commonly observed in people receiving other shots such as the tetanus or chicken pox vaccines

Praveen Buddiga, an immunologist based in the San Fernando Valley, told CBS8 he sees this kind of hypersensitivity in 2-9% of patients receiving shots and gives them some simple advice.

"Just use the method of putting ice on it, drink a lot of water, and stretch that arm and it'll go away in less than 24 hours," Buddiga told the outlet.

The rash isn't a reason to avoid getting vaccinated or request a certain shot

Kara Leeper, a speech therapist living in Los Angeles, told CBS8 she had a rash suddenly show up eight days after she got one of her Moderna shots. She described it as a "a big red bull's eye rash" that "itched and hurt and was warm to the touch."

The rash went away within 48 hours, and while it was uncomfortable, Leeper encouraged others to get their second shots.

Freeman said the same, adding that such a minor reaction is not a reason to avoid the Moderna vaccine entirely.

"It doesn't mean you should get Pfizer instead of Moderna," she said. "It's not such a big deal."