Why Does Sweat Leave Yellow Stains After Drying Even Though It Is Colorless?

Table of Contents (click to expand)

The reason why your light-colored clothing has yellow stains where you’ve been perspiring is just basic science involving bacteria on your skin, the clothes you wear, and possibly what kind of deodorant you use.

Have you ever wondered why your clothes develop those pesky yellow stains after you’ve been sweating and the moisture has dried? It’s a peculiar phenomenon, considering that sweat itself is colorless. What’s behind this unwanted transformation?


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What Is Sweat And Why Is It Colorless?

Sweat is a way for the body to cool off. There are two types of sweat, produced by different sweat glands. Eccrine glands, found all over our body, produce sweat that’s mainly made of water. Apocrine glands are mainly found in our armpits and groin area, and these produce sweat that contains fat droplets, ammonia, and proteins. Both of these types of sweat, upon secretion, are odorless and colorless.

So… why does that colorless secretion leave yellow stains when it dries up?

Eccrine_gland
Structure of Eccrine Gland (Photo Credit: OpenStax College/Wikimedia Commons)

Bacteria And Fungi On The Skin

The answer lies in certain substances present in sweat. The salt, urea, and ammonia in sweat are ingested by the bacteria or fungi that live on you skin. The bacteria metabolize these compounds in sweat and release new molecules, some of which have a yellowish color. The moisture, and the nutrients in sweat, are ideal for your skin’s microbes.

Deodorants and antiperspirants can also react with molecules in sweat to form a yellow color. Many deodorants contain aluminum, which can react with the proteins in sweat to cause yellow stains.

Types Of Clothing

Certain fabrics, like polyester and nylon, can trap sweat and bacteria against our skin. This can lead to yellow stains on lighter clothes. This is especially common in areas where sweat tends to accumulate, like our underarms.

To prevent this from happening, try wearing clothing made from breathable fabrics, such as cotton or bamboo. These fabrics will help wick sweat away from your skin and allow it to evaporate more easily. This helps in preventing yellow sweat stains from developing.

Also Read: Why Do Some People Sweat More Than Others?

Some Medical Conditions That Cause Yellow Sweat

  1. Chromhidrosis: Individuals with chromhidrosis have yellow, green, blue, brown, or sometimes black sweat, due to the deposition of a pigment called lipofuscin in their sweat glands. It mainly affects the face and underarms.
  2. Pseudochromhidrosis: It causes unusual sweat color after coming in contact with chemicals, dyes, or bacteria (chromogenic bacteria).
  3. Hematohidrosis: In this condition, a person’s sweat contains blood

In the case of any of these medical conditions, one should immediately consult a healthcare professional.

Conclusion

So, there you have it! The reason why your light-colored clothing has yellow stains is just basic science involving the bacteria on your skin, the clothes you wear, medical conditions, and possibly what kind of deodorant you use. All these factors could be the reason why you have yellow stains on your clothes. The best way to avoid them is to clean yourself regularly, wear light cotton clothes, and use aluminum-free deodorant. And next time you notice those yellow sweat stains, remember that it’s not the sweat itself, but the chemical interactions at play. Stay cool and stay fresh!

Also Read: Why Do Clothes Smell If Not Dried Properly?


References (click to expand)
  1. Di Giorgi, A., Sprega, G., Poyatos, L., Papaseit, E., Pérez-Mañá, C., Di Trana, A., … Farré, M. (2023, April 17). Sweat Testing for the Detection of Methylone after Controlled Administrations in Humans. International Journal of Molecular Sciences. MDPI AG.
  2. Koley, S., & Mandal, R. (2016). Red and black pseudochromhidrosis. Indian Journal of Dermatology. Medknow.
  3. D Wilkes. (2021) Chromhidrosis - StatPearls.
About the Author

Shatakshi is a bioinformatics expert with a passion for neurobiology. She earned her M.S. in Bioinformatics from Banaras Hindu University and has since been dedicated to exploring the intersection of biology and computer science. She enjoys immersing herself in the pages of fantasy romance novels, discovering new worlds, and experiencing grand adventures from the comfort of her armchair. Despite her love of sedentary activities, she is also determined to stay active and is currently learning how to swim.

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