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What Causes Pit Stains? Yellow Armpit Stains Explained

November 06, 2020 4 min read

what causes pit stains

Pit stains are the pits. Countless shirts have been ruined because of them. Let's face it, the phenomenon of armpit stains is quite common. But don't fret. The problem is easy to resolve if you know what causes it. Keep reading as we explore what causes armpit stains and what you can do to stop them. 

The Basic Science of Pit Stains

As the famous idiom goes “know thy enemy.” Before you try getting rid of armpit stains, it is important for you to understand how they happen in the first place. While the reasons may vary, oftentimes pit stains occur for a singular reason: a chemical reaction. 

When your sweat glands activate, they produce a watery substance that contains several different elements, including protein. These proteins produced by sweat often react with the chemicals in an antiperspirant, like aluminum. This reaction results in the yellow-like pit stains on the clothes you’re wearing.

What Causes Pit Stains?

Oftentimes, there are nefarious factors that contribute to the armpit stains ruining your shirts. The composition of your sweat, its interactions with antiperspirant, your state of mind, and laundering habits are all culprits.


As mentioned, the most common reason for yellow pit stains is a chemical reaction between your sweat and antiperspirant. Specifically, when the aluminum in antiperspirant interacts with the proteins from your sweat. The two elements mix and rub against the fabric of your shirt causing a yellow stain.

Because aluminum is the most common ingredient in antiperspirants, pit stains may be a phenomenon you've dealt with for many years. You may have noticed the stains are worse on certain fabrics, like cotton.


The state of being stressed out is commonplace for a lot of people. However, stress (and anxiety) can take its toll on your life in ways you may not have ever imagined. For example, the stress hormone, cortisol, is released in situations when you are nervous or anxious. Stress sweat is different than normal sweat caused by heat or exertion. Its composition is even different, which can cause armpit stains (and an offensive odor).

Poor Clothing Care

When considering what causes yellow armpit stains, take an honest look at the way you launder your clothes. Even if you diligently wash dirty clothes each week, it may not be enough. For example, if you don’t treat and wash soiled clothing immediately, stains and body odor will set into the fabric. When that happens, it can be much more difficult to get rid of them.

It is also important to look at the ways you are treating your stains. Not all commercial stain-removal products get out those embarrassing yellow marks.

Taking immediate action is the best way to care for your sweat-stained clothing.


Believe it or not, sunshine is a lessen-known culprit when it comes to armpit stains. While sunshine is not harmful by itself, it may present a problem if the remnants of detergent on your clothes react with sunshine while hanging dry outside. Sometimes clothing is not properly rinsed or there is residue after washing. If you encounter this problem, avoid hanging clothes outside or switch detergents. If this is not possible, then use a low or air temperature setting on your dryer, or hang clothing inside on a clothes rack.

3 Ways to Stop Pit Stains

Wear a Sweat Proof Undershirt

The best way to protect your clothing from armpit stains is to stop sweat from making contact in the first place. Wearing a traditional undershirt may help if you don’t sweat much. But if your regular undershirt isn't enough, then try an Ejis sweat proof undershirt (available in our shop or on Amazon).

Our sweat proof undershirts block sweat from reaching your clothes. A waterproof layer stops sweat from transferring to your shirt, which prevents underarm marks and stains. Additionally, the fabric of our undershirts is infused with real silver to fend off odor-causing bacteria.

how to get rid of sweat stains

Try a Different Antiperspirant or Deodorant

We've already established that reaction between sweat and the aluminum used in antiperspirants is what causes most armpit stains. We've also learned that aluminum is the most common ingredient in antiperspirants. If you sweat a lot, you may not be able to switch from antiperspirant to deodorant. (Deodorant is made to mask body odor, not stop sweat.)

Instead, look for an antiperspirant that is aluminum-free. There are all-natural antiperspirants that rely less on chemicals. Check out some of our recommendations for the best aluminum-free antiperspirants.

Properly Launder Your Clothes

Taking immediate action is the best way to care for your sweat-stained clothing. Here are a couple of tips to help you establish a good laundering routine.

  • Immediately wash your offending shirts and other sweat-stained clothing. If you don’t have time for an entire wash cycle, then you can rinse the stains in cold water. Hang in a well-ventilated area until you can properly treat and wash your clothes.
  • Treat the stain immediately. We’ve done the research, and we've collected pit stain treatments using common household products. There also are a few commercial products that are effective in removing pit stains, like Raise Armpit Stain Remover or OxiClean. 
  • Avoid line-drying in the sun. Instead air-dry in the dryer or hang dry on a rack inside.

We can all agree. Armpit stains are embarrassing, frustrating, and costly if they are not properly treated in time. But now that you know what causes pit stains, you can be more proactive at avoiding them... like wearing an Ejis sweat proof undershirt. 

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