The Science Behind Armpit Stains & How to Stop Them

Are you bothered by pit stains on your shirts? We’ve all been there. When you raise your hands or lift your arms, it’s embarrassing to reveal yellow stains.

But pit stains don’t have to plague your day-to-day life. Read on to learn the science behind underarm stains and the best ways to prevent armpit stains from ruining your clothing.

In this guide, we'll cover:

What Causes Armpit Stains?

News flash: It’s not just sweat. Pit stains occur when the proteins in your sweat react with aluminum and other chemicals in your antiperspirant.

Sweat, on its own, is odorless and colorless. Apocrine sweat glands, found in your underarms, produce a different type of sweat than eccrine sweat glands (found elsewhere on your body). Unlike eccrine sweat, apocrine sweat is full of fats and proteins, contributing to stains and odor.

Aluminum is the active ingredient in most over-the-counter and prescription antiperspirants. Unfortunately, as your armpit sweat mixes with the components of your antiperspirant, the result is a pesky yellow pit stain that’s tough to get out.

Understanding how stains form helps you prevent sweat stains entirely. Here are some leading causes that contribute to those pesky sweat stains.


We all do it: You toss your sweaty shirt directly into the hamper until laundry day. But this creates a breeding ground for yellow stains, which are especially noticeable on white clothing.

The more time sweat and aluminum have to soak into your shirt, the more difficult sweat stains are to remove.

Many people make the mistake of bleaching their white shirts to get yellow pit stains out, but that makes the stains much worse.


A rare medical condition called chromhidrosis could also cause pit stains. People with chromhidrosis have yellow, green, blue, brown or even black sweat caused by a pigment produced in the sweat glands called lipofuscin.

People with chromhidrosis have higher lipofuscin concentrations or a higher-than-normal level of lipofuscin oxidation.

Other causes of discolored sweat include:

  • Pseudochromhidrosis: Unusually colored sweat that forms after contact with chemicals, dyes, or bacteria that produces pigments (chromogenic bacteria).
  • Hematohidrosis: Sweat that contains blood
  • Excess bilirubin: Orange-yellow pigment produced by the liver
  • Infection
  • Poisoning

If you notice these symptoms, consult your healthcare provider or dermatologist.

Do Armpit Stains on Shirts Come Out?

For those who struggle with armpit stains on shirts, laundry day is a burden. Pit stains can be difficult to remove, and throwing away a shirt that’s otherwise still in good shape is wasteful.

If treated correctly (and quickly), armpit stains have a good chance of coming out of your clothing. But if you’ve sweated profusely in a shirt and let the shirt sit without treating it or have had stains set into your shirt over time, you’ll have a much harder time getting them out.

Read How to Get Sweat Stains Out of Shirts: Tips and Tricks

How to Stop Pit Stains

The best defense is a good offense. Here are several ways to stop pit stains from forming.

  • Wear a sweat proof undershirt for protection. A sweat proof undershirt is the easiest, most hassle-free way to stop pit stains from ruining your clothes.
  • Change your antiperspirant or deodorant routine. You may be applying antiperspirant incorrectly or using a product that isn't suitable for your needs.
  • Take care of your clothing. By following proper laundry protocol, you can reduce the occurrence of pit stains or make them much easier to remove.
  • Shave or trim your armpit hair. Cutting armpit hair can keep moisture and sweat from accumulating and causing stains.
  • Consider natural remedies. Supplements like vitamins B, C, and E, witch hazel, sage, brewer’s yeast, eucalyptus, lecithin and chamomile are thought to have sweat-reducing properties.
  • Use natural deodorant. Choosing deodorant (not antiperspirant) without aluminum eliminates the cause of yellow stains.
  • Avoid eating sweat-producing foods. Spicy foods can trick your nervous system into believing you’re hot, kicking your sweat response into high gear.
  • Watch your vices. Drinking alcohol and caffeine and smoking cigarettes can send signals that raise heart rate and body temperature, signaling your central nervous system to sweat more to cool down.

Read more on how to prevent pit stains from ruining your shirts

Say Goodbye to Pit Stains With Thompson Tee

The best way to prevent pit stains from ruining your shirts is to stop sweat at the source. The second best way is to wear a Thompson Tee.

When you want extra protection, count on Thompson Tee as your best line of defense against sweat stains. Thompson Tee’s patented Hydro-Shield® sweat proof undershirts are guaranteed to stop 100% of sweat stains and embarrassing odor from seeping through and ruining your favorite shirts or outer clothing layers.

Buy a Thompson Tee to get rid of pit stains

Ready to prevent sweat stains for good? Try a Thompson Tee risk-free!