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What are the Most Common Causes of Cysts in the Underarm?

By K. Gierok
Updated Mar 03, 2024
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Those who develop a cyst in the underarm often view it as a symptom of a very serious illness. While cysts can be indicative of serious health conditions, they most commonly are caused by a number of various infections with varying degrees of seriousness. The most common type of infection that can lead to cysts are bacterial infections, though viral infections, such as the common cold, are also to blame. In some cases, cysts in the underarm may be caused by breast cancer. Those who have a family history of breast cancer should seek medical assistance immediately if they find cysts in this area.

One of the most common causes of cysts in the underarm has been found to be bacterial infection. Typically, these infections occur primarily due to antiperspirant use or shaving with a dirty razor. Those who develop a cyst after switching to a new brand of antiperspirant or deodorant should consult with a dermatologist in order to make sure that this is, in fact, the cause of the cyst. In addition, those who notice an increase in the rate of occurrence of cysts after shaving should consider switching to a new razor, or looking for a different brand of shaving cream. In some cases, a new shaving technique must be used in order to prevent infection.

In some cases, an infection that has been left untreated can lead to the development of an abscess. An untreated infection can cause the cyst to grow to a surprisingly large size, and can be very painful to the touch. While an abscess can often be treated through the use of prescription medications, in some cases, surgery or other more aggressive forms of treatment may be required.

A viral infection may also lead to the development of cysts in the underarm. Viral infections that can cause this condition typically include the common cold, influenza, or other similar respiratory conditions. Often, once the primary condition has been treated, the cysts will also go away.

One of the most serious causes of cysts in the underarm is breast cancer. Typically, these cysts grow relatively slowly, and are small and very hard. Those who have a family history of breast cancer and who develop cysts should seek medical assistance as soon as possible. While not all tumors are cancerous, it is important to make a diagnosis as soon as possible for the best results.

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Discussion Comments

By anon998988 — On Oct 03, 2017

@ceilingcat: Yes "they" do tell you to also check the armpit area when doing a self-breast exam, as the breast tissue extends up into that area. It's your doctor that didn't tell you, not "they". But, as women, we should take the time and learn about our own anatomy. No one is going to better care for us than ourselves because we know ourselves better than anyone because we feel everything we go through every day. You can't put everything on a person that sees you once in a while. But, then most of us learned about our breasts in sex ed classes and health classes in school. Well, at least I did.

By anon947306 — On Apr 25, 2014

As part of an elimination programme, I would recommend switching to a crystal deodorant as they are naturally antibacterial and don't clog pores. I have used Salt of the Earth for years.

By ceilingcat — On Dec 29, 2012

@starrynight - Glad your friend is OK. MRSA is definitely not a joke, and I know some people die from it.

Anyway, I didn't know that a small cyst under your arm could be from breast cancer. I wonder why they don't usually tell you to check under your armpits when you do a monthly breast check for lumps?

By starrynight — On Dec 28, 2012

A friend of mine ended up with an abscess under her arm from having a MRSA staph infection. She had them a few other places on her body as well, but the abscess under her arm ended up being the worst.

She had to go on several rounds of antibiotics, and go to the doctor several times to get the abscess drained. The whole process took awhile, but she is fine now thank goodness.

By KaBoom — On Dec 28, 2012

@eidetic - I probably would have panicked in your situation too. I'm glad you were able to get a doctors appointment the next day though.

Anyway, I once had an actual cyst under my armpit. It ended up being caused by an ingrown hair that I had picked at and plucked out. The hair follicle got infected, causing a cyst.

By eidetic — On Dec 27, 2012

I have a funny story related to underarm cysts, although it wasn't very funny to me at the time. When I was in college, I had a really bad cold. My lymph nodes were really swollen in my throat, which is to be expected.

One night, I noticed a lump at the very bottom of my underarm area somewhat near my breast. I panicked and went to visit my doctor the next day.

When she examined me, she told me it was just a swollen lymph nodes. There are lymph nodes under your arms, and they can get swollen with illness just like the ones in your neck. I was so relieved.

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