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If You Have a Skin Reaction to the Moderna COVID-19 Vaccine, Don't Panic

Skin reactions to Moderna vaccine.

Courtesy of Kimberly Blumenthal, MD

Key Takeaways

  • Researchers are calling for greater awareness of skin reactions that can appear days after getting the Moderna COVID-19 vaccine.
  • While unsightly and uncomfortable, the reactions usually resolve within a few days and do not pose any long-term health risks.
  • If you develop a reaction, the researchers recommend treatment with basic over-the-counter anti-allergy medications. They also stress that concerns about a skin reaction should not keep people from getting vaccinated.

In a letter to the editor published in The New England Journal of Medicine (NEJM) on March 3, 2021, researchers reported on a dozen people who developed erythema (redness), induration (swelling), tenderness, or some combination of the three at the injection site between four and 11 days after receiving their first dose of the Moderna COVID-19 vaccine.

While immediate reactions to the COVID-19 vaccines are common, the researchers want people to know that delayed skin reactions can also show up days to weeks after they get the shot.

What Do the Reactions Look Like?

The delayed skin reactions often resembled the raised, red welts that are caused by an insect sting. However, according to an index included in the letter, the reactions' appearances were noticeably variable.

One of the 12 reactions described in the report.
Courtesy of Kimberly Blumenthal, MD

Kimberly Blumenthal, MD, lead author of the paper and co-director of the clinical epidemiology program in the division of rheumatology, allergy, and immunology at Massachusetts General Hospital, tells Verywell that the skin reactions can be “as large as almost 20 centimeters, taking up most of the upper arm.” However, the areas can also be much smaller.

How Long Does the Reaction Last?

While short-lived, these skin reactions can cause significant discomfort and “are likely to generate concerns among patients and requests for evaluation,” the researchers write, recounting a case in which a reaction was mistaken for the bacterial infection cellulitis and medicated with antibiotics.

Given the considerable potential for confusion, the researchers are calling for increased clinical awareness of these skin reactions to help avoid needless diagnostic testing and treatment.

Photo of an arm rash.
Courtesy of Kimberly Blumenthal, MD

The authors hope that their letter will help patients and physicians recognize these reactions if and when they occur.

What This Means For You

If you get the Moderna COVID-19 vaccine, there is a small chance that you could develop a skin reaction. If you have itching, swelling, or tenderness at the injection site in the days after getting either dose of the vaccine, don't panic. The swelling typically goes down in about two to 11 days. To relieve symptoms, experts recommend taking an antihistamine and using a topical steroid for any itchiness, swelling, and redness. You can also apply ice for swelling and pain at the site of the shot.

How Common Are the Reactions?

The reactions were first observed during a phase 3 clinical trial of the Moderna vaccine. In a study published in the NEJM in February, 2021, the investigators reported that 12,765 (84.2%) of the 15,168 participants who had received the vaccine rather than the placebo developed an immediate skin reaction after receiving their first dose of the vaccine.

By contrast, 244 (0.8%) developed a delayed skin reaction—defined as a skin reaction that appears eight or more days later—after getting their first dose, and 68 (0.2%) developed a delayed skin reaction after getting their second dose.

Reactions Could Be More Common Than Statistics Show

Rebecca Saff, MD, PhD, another lead author of the report and allergy fellowship director of the allergy and clinical immunology unit in the division of rheumatology, allergy, and immunology at Massachusetts General Hospital, tells Verywell that in the trial, "adverse events, including local adverse symptoms, were solicited for the seven days after the vaccine was given and unsolicited for 28 days after the vaccine, meaning that many of the more mild reactions may have been missed if they were after day seven."

The statistics suggest that a small minority of people—fewer than one in 100—are at risk. However, the actual percentage is likely higher. 

In the letter, the researchers described how and when the skin reaction manifested in people between the ages of 31 and 61—the majority of whom were white and female. The authors explained that the small sample size limited their ability to identify any differences in the appearance of the reaction between races and ethnicities. 

“We saw the reactions on different skin tones but did not see any reaction on dark skin," Saff says. "We are still recruiting volunteers into our registry and hope we can recruit a diverse group of participants so we can understand reactions on all skin tones."

Why Do the Skin Reactions Happen?

Based on the results of a skin biopsy, the researchers' best guess is that the skin reactions are likely caused by delayed T-cell-mediated hypersensitivity—an intense immune response that begins a minimum of 12 hours after contact with a pathogen or allergen, meaning an infectious or irritating substance. 

“We have a lot of things that are delayed hypersensitivity, like eczema, contact dermatitis, common antibiotic rashes," Blumenthal says. "There may be genetic factors at play—we know that genetics can be a risk for certain T-cell reactions to drugs—but otherwise, we don’t fully understand why someone has a response while another does [not] for most drugs and vaccines."

What to Do if You Have a Reaction

Worry over having a skin reaction should not deter you from getting a COVID-19 vaccine. If you do develop one, don't panic. While it may cause you discomfort, it's likely not serious and should resolve on its own in a short time (about two to 11 days, according to the study).

If you’re finding the symptoms hard to bear, Saff recommends several basic home remedies and over-the-counter (OTC) medications for relief. Specifically, “we would recommend taking an antihistamine such as fexofenadine or cetirizine and using a topical steroid for the itch, swelling, and redness," Saff says. "Ice can also be helpful for the swelling and pain at the site."

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  2. Baden L, El Sahly H, Essink B, et al. Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine: supplementary appendix. N Engl J Med. 2021:384(5). doi:10.1056/NEJMoa2035389

  3. Baden L, El Sahly H, Essink B, et al. Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. N Engl J Med. 2021:384(5):403-416. doi:10.1056/NEJMoa2035389