Lump in the Armpit: When should you Worry?

It's important to stop using antiperspirant deodorizers if you want to avoid unwanted lumps in the armpits. If you do use them, make sure you remove them at night to let the skin breathe.
Lump in the Armpit: When should you Worry?
Valeria Sabater

Written and verified by psychologist Valeria Sabater.

Last update: 11 June, 2022

It’s a common problem. We’ve all probably found a lump in our armpit at some point and it shouldn’t cause you a disproportionate amount of alarm. Here, we’ll explain what steps you should take the moment you find a lump.

What could cause a lump in the armpit to form? 


Eighty percent of cases are normal and shouldn’t cause any problems. The first thing you should do when you find a lump is not be frightened because it’s probably due to a type of furunculosis. And what exactly is furunculosis, you might ask? Here are some basic guidelines to understand this:

The most common cause of underarm lumps: furunculosis

self check

The most common cause of the formation of a lump in the armpit is furunculosis. This is simply an inflamed hair follicle, commonly known as a “pintail.” It’s painful and can be scary when detected. It is usually due to an infection of a sweat gland caused by an ingrown hair. When sweat can’t escape the follicle, bacteria accumulates quite quickly. Larger or smaller bumps may appear as a result.
Although not usually harmful, a lump can become very annoying. Sometimes it goes away on its own, but others can form very serious cysts that require appropriate treatment. A doctor will usually prescribe antibiotics to protect against a staphylococcus infection. But if that doesn’t resolve it, more will be needed to remove the cyst.
What can you do to prevent these cysts or pintails from forming under the arms? Well, unfortunately some people are just more prone to them than others, and if you’ve had them once they’ll more than likely reappear.There are some antiseptic creams that can help slow their formation, but the best solution is to be extra careful with hair removal methods – especially shaving.
Whenever you shave you risk these little pests appearing, because hair can become trapped in the follicle. Try washing and exfoliating the skin under the arms first to allow the pores to open. And don’t use aggressive chemical-based deodorants because they can damage this sensitive area.  Generally, this is the most common cause of a lump in this region.

Second most common cause: swollen lymph node


Don’t be frightened. Inflammation of a lymph node is known as lymphadenitis. As you’re probably aware, there are a lot of lymphatic vessels under the arm, moving lymphatic fluid through the bloodstream as a cleansing and filtration agent. This helps your body fight off infections.

But sometimes when our defenses are weakened or we’ve contracted a virus, our lymphatic glands can become inflamed or swollen. Hence a lump in the armpit. Lymphadenitis can especially occur after skin infections or other bacterial infections. So what do you do when you find out you have a swollen lymph node?
Well, the first step is to have an analysis of the lymphatic fluid to determine the cause of the inflammation and any bacteria that’s present. This is done by drawing a little fluid out of the gland. The area is slightly numbed so this procedure isn’t painful.
Your results will tell you what caused the inflammation and indicate what treatment you should follow to resolve the issue.

Cause number three: lymphoma

This is a possibility. When you find a lump in the armpit there’s a small chance it could be due to an inflamed lymph node that originates because of lymphoma. Among the types of lymphoma are “non-Hodgkin’s lymphoma” and “Hodgkin’s lymphoma.” These are both varieties of cancer, and treatments are very effective.
Survival rates from non-Hodgkin’s and Hodgkin’s lymphoma are 90% and 70%, respectively. Both kinds of lymphoma are generated by a type of white blood cell called B lymphocytes (or B cells), and that’s how doctors test to find out if someone has one of these diseases.
This type of cancer requires multiple sessions of chemotherapy, but of course each person is unique and not everyone will require the same number of sessions or length of recovery time. Today there are many advances in the science surrounding cancer, and we need to remember to have hope – this is a disease that requires a lot of personal effort, courage, and support from family and friends. You can beat it.

How do I know if my lump is due to furunculosis or lymphoma?


The first thing to do is to stay calm and not stress yourself out. Anytime you find a lump under the arm it’s best to consult a doctor as soon as possible. Lymphomas are also usually associated with a low-grade fever, problems with sleeping, night sweats, and weight loss.
But because you might not have any of these other symptoms, go to your doctor first. And don’t worry – the vast majority of cases are due to the formation of a simple cyst caused by a hair follicle.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

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  • Murillo, C., Escobar, P., Fuentes, E., & Alvarado, J. S. (2007). Linfoma y su expresión en patología mamaria. Rev Obstet Ginecol, 2(1), 49-52.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.