You asked, we answered: Why do my lymph nodes swell after vaccination?

Woman touching her armpit


My lymph nodes in my armpit swelled after the COVID-19 vaccine. I just got the flu vaccine and my armpit lymph nodes are swelled again. Is this normal? Why does this happen? 

Answer from radiologist Elizabeth Edney, MD:

Temporary lymph node swelling after receiving the COVID-19 or flu vaccine is a normal, expected reaction. 

Lymph nodes are small, bean-shaped glands that are part of your immune system. Lymph nodes are present throughout your body, but clusters of them are found in the armpits, neck and groin. 

When you receive a vaccination, your lymph nodes are activated to produce white blood cells, which fight off infection. This causes the lymph nodes to swell and, possibly, to become noticeable to the touch. This swelling normally goes away a few weeks after receiving the vaccine.

Because of the potential for swelling, consider waiting to schedule a mammogram for several weeks after receiving your COVID-19 vaccine. When you get your mammogram, let your doctor know when you had your vaccine shots and on which side (left or right arm).