‘Covid Arm’ Rash After the Moderna Shot Is Common but Not Worrisome
Reactions frequently occur after vaccines while the immune system is doing its thing
About five days after I got my Moderna vaccine, I found myself scratching the place where I’d gotten it. At first it was automatic, like scratching any itch, but soon I realized it was really itchy — and big and warm and red. I knew there could be injection site reactions, but with all my past vaccines, it had only been red or swollen at the injection site for a day or two after the shot. This was a week later, which seemed weird.
It turns out it isn’t as weird as I thought, and it’s something many others, though mostly women it seems, are experiencing as well.
“I was concerned that I might be having some kind of allergic reaction, so I posted this picture and asked if I should contact my doctor,” said Amanda (last name withheld by request), who experienced it after her first dose. But her friends and the nurse who gave her the second dose said it wasn’t anything to worry about.
These reactions were reported in the clinical trials but only rarely: 0.8% of participants reported one after the first dose and 0.2% after the second dose. The formal term is delayed cutaneous hypersensitivity — a type of minor allergic immune response that can occur after other drugs as well — but many are just calling it “Covid arm.” (I find this ironic since it’s more like “anti-Covid arm” if it’s from a vaccine!)
A case series of 12 people reported in a letter to the New England Journal of Medicine March 3 found evidence that the hypersensitivity results from activation of T cells, the immune cell type that trains B cells to build antibodies and that causes virus-infected cells to self-destruct. That’s good news because it suggests the vaccine brings about immunity through T cells as well as antibodies. That also may explain why it takes longer — four to 11 days after injection in the study — to show up; T cells don’t ramp up overnight.
Developing the reaction after the first dose was not a counter-indication to getting the second dose, the researchers wrote, and six of the 12 patients did not have a reaction after their second dose. Three had a similar reaction as the first time, and three had milder reactions, with the rash starting a few days earlier in all six. One of the patients had received antibiotics because the rash was misdiagnosed as cellulitis, pointing to the need for people to recognize that this reaction can occur. It’s not a skin infection and does not require antibiotics. Most treated the rash with ice and antihistamines, though a few received topical or oral steroids.
The reactions faded about a week after showing up in the NEJM study, with the longest lasting 11 days, but in some people, the irritation has lasted longer. Beth Brown described hers as “huge, red, and hot, with occasional itchiness,” and it was still slightly painful 20 days after her vaccine. But she shared her photo online to normalize vaccine reactions because she felt it was important for people to know these reactions can occur and aren’t concerning.
Not a reason for concern
The reaction appears to occur more frequently in women, but it may be that women are simply reporting it more often. The vast majority of these reactions follow the Moderna vaccine, though one friend of mine experienced it after the Pfizer shot. She described it exactly the way I experienced it: a broad, raised lump that was red, warm, and itchy, much like a spider bite. For most people, it starts small, about the size of a dime or quarter, and grows over a few days to sometimes as large as a pancake. Mine only reached about four inches across, but some reach up to five or six inches.
I reached out to friends to see who else had experienced this reaction and was overwhelmed with how many others — all women — had it. It startled some people who were anxious about it at first, but others shared photos of theirs on social media to normalize the fact that reactions frequently occur after vaccines while the immune system is doing its thing. For many, it’s mostly just annoying, but it can be especially painful for others.
For Donna Tinkler of Boiling Springs, Pennsylvania, the reaction began the Monday morning after getting her second shot on Saturday.
“I woke up and I had a red circle maybe the size of an orange,” she said. It grew larger and larger and became itchier by the day. “I felt like I wanted to rip my skin off,” she said. She contacted her doctor and was relieved to find out it was a normal reaction and that some oral Benadryl and ice packs could relieve the discomfort. Now she’s just grateful that’s the only side effect she experienced.
“I’d rather having the itching and redness rather than end up in the hospital on a breathing machine,” Tinkler said. “This is a small price to pay for getting something that might take my life.”
Dian Darr, a retired teacher in Texas, was similarly taken off guard by the reaction when it happened five days after her shot.
“I woke up with horrible itching at vaccine site. Within hours there was a large red ring around the site, and the arm was warm to the touch. It felt awful,” she said. She said it was the worst itching she had ever experienced — including poison ivy — but she’s not sorry she got it.
That’s the reaction I’ve heard from everyone I’ve spoken to so far. Certainly it’s annoying, sometimes miserable or painful, but not enough to dissuade people from the shot, and it’s not a reason to be concerned. Several were comfortable sharing their photos and experiences below.
“The shot was 100% worth it. I’d do it again for sure just to have some peace of mind about being able to be healthy for my family,” Kristen Kitchens of Houston, Texas, said. “I have a 10-month-old son and am breastfeeding him and even felt safe with that after reviewing all the literature and recommendations.”
What to do if you experience this skin reaction
If you develop this reaction, you don’t have to do anything, but several treatments can make you more comfortable. Ice packs can help ease it, and it’s fine to take a pain reliever or anti-inflammatory, such as ibuprofen or acetaminophen (Tylenol) for pain. Hydrocortisone or antihistamine cream or oral antihistamines (such as Benadryl) can reduce the itching. If the itching is especially intense, your doctor may prescribe topical or oral steroids. The CDC is attempting to track these reports, so those who experience it can report it here.