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My gym clothes retain an unpleasant musk even after washing them with warm water and detergent. I've experimented with soaking my gym clothes in salty water before washing them. My hypothesis is that the high salt concentration will cause plasmolysis in the cells of the bacteria. It has worked with mixed results; I'm never sure how much salt I should add or how long to soak the clothes.

I've looked for answers but I can only find papers with highly technical results.

(1) Can the odor-causing bacteria be killed with a salt treatment?

(2) If so, what concentration of table salt is needed?

(3) How long does the treatment need to last for plasmolysis to occur?

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  • $\begingroup$ Lack of water and UV are great - Always let them hang outside right after use, never let them incubate in your sports bag and sunlight is devastating to microorganisms. $\endgroup$ – AliceD Jul 1 '15 at 3:55
  • $\begingroup$ Specifically, hang them outside in the bright sun. You can soak your clothes is soap water or a mild perfumed disinfectant like dettol. $\endgroup$ – WYSIWYG Jul 1 '15 at 4:37
  • $\begingroup$ @WYSIWYG - is this question answerable without knowing the exact microfauna inhabiting OPs skin/clothes? $\endgroup$ – AliceD Jul 1 '15 at 4:48
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    $\begingroup$ @AliceD Can be difficult because usually normal washing is sufficient unless the clothes have taken a long time to dry (rains etc). In such cases molds also start growing on clothes. In any case I am not sure if this salt method would be effective. $\endgroup$ – WYSIWYG Jul 1 '15 at 4:56
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    $\begingroup$ You should keep in mind that the odor is a mixture of stale sweat and chemicals produced by microorganisms, not necessarily the microorganisms themselves. Basically, by the time the odors appear, it's already too late. Thorough washing and immediate drying of your clothes after exercising can help mediate the accumulation of additional odors, but what's there is there. These aromatic organic compounds can bind very tightly to the fibers of the cloth, and are quite difficult to get rid of. Bleach may help, depending on the type of fabric (and color), but I doubt salt will do much of anything. $\endgroup$ – MattDMo Jul 1 '15 at 13:40
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Short answer
Toxicity of salt depends on contact time. 50 g NaCl per liter kills nearly all bacteria in 2 days. 100 g NaCl/L may do a quite thorough job in 30 minutes.

Background
Body odor is caused by bacteria that feed on the fluids produced by the apocrine glands, mainly present under the arm pits and other areas with abundant hair follicles. Bacteria in the skin feed on the products of the apocrine glands and convert it into odorous compounds. Skin microfauna includes Staphylococcus, Micrococcus, Corynebacterium, Dermabacter and others. As pointed out by others in the comments, treating your cloths against bacterial growth may not be the most efficient approach, as the bacteria are residents of the skin. Nonetheless, the following studies addressed the antimicrobial effects of salt.

A study using the gut bacterium E.coli showed that survival in 5% NaCl (50 g NaCl per liter H2O) was <0.01%. In 2% NaCl survival survival was 8%. The contact time was 48 hours (Carlucci and Pramer, 1958).

Another study examined the effects of salinity on E. coli using a shorter contact time of 30 minutes, and concluded that 10% salinity killed 80% of organisms (Somani et al., 2011).

Sea water, which has a salinity of about 3.5% contains low numbers of bacteria (Carlucci and Pramer, 1958), suggestive of toxic concentrations of NaCl, the major salty constituent in sea water.

Although E. coli has been associated with skin fauna and body odor, I must note that Gram negative gut bacteria as used in the two studies above may not be representative of the mainly Gram positive microfauna found on the skin (Strauss & Kligman, 1956).

References
- Carlucci and Pramer, Am Soc Microbiol (1958)
- Somani et al., J Eng Res Studies (2011): 40-43
- Strauss & Kligman, J Invest Dermatol (1956); 27: 67–71

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  • $\begingroup$ 5% NaCl is 5g/100mL $\endgroup$ – canadianer Jul 1 '15 at 17:03
  • $\begingroup$ well, approximately yes, but to be exact 5g/100mL is probably less than 5%, though the difference should be quite small. @AliceD is it probable that skin flora have adaptations to make themselves more resistant to salt since they live on skin which easily gets sweaty? $\endgroup$ – busukxuan Jul 4 '15 at 15:41
  • $\begingroup$ @busukxuan good question! $\endgroup$ – AliceD Feb 22 '17 at 19:03
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    $\begingroup$ @busukxuan Biologists often use w/v concentrations. 1% w/v is defined as 1 g / 100 mL. According to Wikipedia, the sodium concentration in sweat is around 15-65 mM (50 mM is ~0.3% w/v). Bacteria should easily tolerate this without special mechanisms. $\endgroup$ – canadianer Feb 22 '17 at 20:00

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