How to Tell if a Stain Is Sperm

Co-authored by Rani Gorgis and Janice Tieperman

Last Updated: July 3, 2024 Fact Checked

Did you find a suspicious-looking stain on some clothing, bedsheets, or other fabric? You can figure out if the stain is semen using simple tests and tools. We’re here to walk you through exactly what to do and what to look for, along with ways to clean away those pesky stains once and for all.

How to Detect Sperm & What it Looks Like

Use a blacklight—if the stain is sperm, it will likely light up.
Check the color. Sperm stains are usually gray, light yellow, or off-white.
Feel the texture of the stain. If it's crusty, it could be sperm.
Remove dried stains with delicate detergent, upholstery-grade stain remover, or enzymatic pre-treatment cleaner.

Section 1 of 3:

How can you detect sperm stains?

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1
Use a blacklight to detect sperm stains. Switch off the lights in the room and hold the blacklight over the material. Guide the light down the fabric and see what appears—in many cases, sperm lights up underneath the lamp. The stain itself may be yellow, blue, or some other color, depending on the exact light that you’re using.^{[1]
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- A blacklight, also known as a Wood’s lamp or UV-A light, shines ultraviolet light over a given surface.^{[2]
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- Keep in mind that a blacklight isn’t a 100% conclusive way of identifying sperm stains.^{[3]
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  PubMed Central
  Journal archive from the U.S. National Institutes of Health
  
  Go to source} Bodily fluids like urine and blood also look bright beneath a blacklight.^{[4]
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Transform your smartphone into a blacklight if you don't have one. Start by covering the LED camera light with a strip of transparent tape and coloring over the lens with a blue permanent marker. Layer another piece of tape on top and color it in with the blue marker again. Then, stick an extra section of tape over top and shade over the lens with a purple permanent marker. Your homemade blacklight is now ready to go!^{[5]
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- This DIY trick is much more useful than a blacklight phone app. While these apps simulate a blacklight, they don’t actually mimic the effects of one.
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3
Get more definitive proof with an at-home test. Use an at-home semen detection kit to test the stain that you spotted under the blacklight—it’ll test the fabric for acid phosphatase (AP), an enzyme found in semen and vaginal stains. Just keep in mind that this test isn’t completely conclusive, since AP is also found in various bodily fluids.^{[6]
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- You can also use an at-home Prostate Specific Antigen (PSA) test to narrow down your results, but this isn’t totally conclusive, either.
- If you’re really curious about the stain’s contents, send a fabric sample to a private laboratory for testing.

Section 2 of 3:

What color are sperm stains?

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Dried sperm stains look gray, light yellow, or off-white. These stains often look shiny and feel stiff to the touch, too.^{[7]
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PubMed Central
Journal archive from the U.S. National Institutes of Health

Go to source} If the sperm is fresh, it might look pale gray, white, or off-white.^{[8]
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Cleveland Clinic
Educational website from one of the world's leading hospitals

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- Dried sperm stains might feel a little crusty, as well.^{[9]
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Section 3 of 3:

How to Treat Sperm Stains

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Clean any fresh sperm stains from regular fabric with cold water. Grab your soiled garments or sheets and stick them under a stream of cold, running water. Steer clear of warm or hot water, though, as this can make the semen stain permanent. Here are some stain removal tips for other materials and surfaces:
- Wool and silk: Soak the garment or sheet in a mixture of water and delicate detergent before sticking it in the washer or hand-washing it.
- Carpet: Dab over the stain with a detergent-soaked sponge. Then, go over the surface with a clean sponge and blot the carpeting dry with paper towels.
- Mattresses: Go over the semen stain with a moist sponge and an upholstery-grade stain remover. Then, blot away any leftover cleaner with a sponge. Dry off the spot-treated section of the mattress with several paper towels.
- Upholstery: Dab at and soak up the stain with a wet cloth. If the sperm stain still doesn’t go away, spritz over the area with an upholstery cleaner. Then, dry off the surface with paper towels.^{[10]
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Treat dried stains with an enzymatic pre-treatment cleaner. Use a bristled brush to scrape away as much of the leftover stain as you can. Once the fabric is mostly clean, soak it in a mixture of water and an enzymatic pre-treatment cleaner. Then, stick the item in the washing machine afterward or wash it as you usually would.^{[11]
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- Opt for a biological detergent when you’re washing the fabric.
- If the item is made of silk or wool, soak it in a mixture of water and delicate detergent. Then, stick it in the washer or hand-wash it as usual.