What Is COVID Arm and What Causes It?

COVID arm is a delayed hypersensitivity reaction that occurs approximately five days after the COVID-19 vaccine. It is characterized by redness, itching, and swelling around the injection site.

Unlike immediate vaccine reactions—like anaphylaxis—COVID arm is generally harmless and resolves with minimal treatment.

This article will discuss COVID arm symptoms and treatments. It will also cover when to contact a healthcare provider.

Symptoms of COVID Arm

COVID arm is a reaction that occurs after a COVID-19 vaccination. The reaction forms a few days to a week after the injection. It tends to be more common after the Moderna COVID vaccine but can happen with the Pfizer vaccine as well.

The symptoms of COVID arm include:

• Red rash around the injection site
• Swelling
• Significant itching
• Sore or pain
• Warmth

The rash may be small, just covering the injection site. However, it can also be quite large, extending over most of the arm. Reports of rash size varied from study to study. One report described a COVID arm rash measuring up to 14 centimeters (cm) in diameter. Another report described the rash measuring 10 cm by 7 cm.

Why Does a Lump Develop on the Arm After Vaccination?

After a COVID vaccination, there may be a small bump where the needle was inserted into the skin. This is a common reaction after vaccinations caused by an immune response to the vaccine or the needle.

The lump can be a good sign that the body is making antibodies against the virus.

Less common is a nodule that develops at the injection site. They are firm and about the size of a pea. There is no redness or pain, and they generally go away without treatment.

Why Does COVID Arm Happen?

COVID arm happens because of a hyperactive immune response to the vaccine. When the immune system senses the vaccine, it builds up defenses to fight the COVID virus, which is exactly the purpose of the vaccine.

However, for reasons unknown to researchers, some people have a more robust immune response to the vaccine and develop COVID arm. Interestingly, a 2021 case report described that the development of COVID arm had no relation to the person's medical history or allergies.

Can COVID Arm Happen After a Booster Shot?

COVID arm can happen after a booster shot.

In a 2021 case study, researchers looked at 15 patients who developed COVID arm with their first vaccination. Eleven of those patients also had reactions to the second dose. Most people developed a reaction sooner after their second dose than they did on the first dose. The duration of the reaction to the second dose was similar to the duration of the reaction to the first vaccine dose.

For those who have gotten COVID arm, their healthcare provider may recommend getting the next shot in the opposite arm.

How Long Does COVID Arm Last?

COVID arm typically begins seven days after the vaccination and lasts about five days. However, it can last up to 21 days.

How to Get Relief From COVID Arm

COVID arm is a reaction to the COVID-19 vaccine that typically resolves with minimal treatment. Taking an antihistamine like Benadryl (diphenhydramine) can help relieve itching. Over-the-counter pain relievers like Tylenol (acetaminophen) or nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil or Motrin (ibuprofen) can help minimize pain.

A cold compress is another treatment option that can help relieve swelling.

If home treatment does not provide relief, contact a healthcare provider for prescription medications or other options.

Why You Should Still Get Vaccinated

Though COVID arm is an unpleasant side effect that some may experience after their immunization, it is not a good enough reason to avoid future COVID vaccines.

COVID arm is not indicative of having a more serious reaction to future vaccines and actually illustrates that the body is mounting a good immune response to the virus.

When to Contact a Healthcare Provider

COVID arm is a localized reaction to the COVID vaccine. When a reaction worsens and causes additional symptoms it is time to contact a healthcare provider.

Immediately call 911 if someone is experiencing a severe allergic reaction. Symptoms of a severe allergic reaction include:

• Difficulty breathing
• Swelling of the mouth, tongue, or throat
• Generalized rash or hives
  

Summary

COVID arm is a reaction to the COVID-19 vaccine. It is more common after the Moderna vaccine and causes redness, itching, and swelling around the injection site.

COVID arm typically develops around one week after the injection and resolves after about five days. Treatment aims to relieve its symptoms with antihistamines and pain relievers.