Having only two types of sweat glands (eccrine, apocrine) I would expect the sweat odor "spectrum" to be very "narrow". However, the smell of sweat greatly varies between scalp, arms, armpits, groin and feet. Why is that?

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    $\begingroup$ I think the odor is caused by bacteria, which vary in diversity across the body. $\endgroup$ – canadianer May 25 '17 at 18:52
  • $\begingroup$ @canadianer why bacteria are so different between armpits vs. groin; hands vs arms; arms vs scalp? $\endgroup$ – Sparkler May 25 '17 at 20:28

Sweat is actually odorless regardless of what type of sweat gland it comes from, of which there are two types - apocrine and eccrine.

As suggested by canadianer, the odor comes from the mixture of bacteria and the resulting sweat. With regards to why your bacterial flora is so diverse is likely due to the different micro-environments found around your body.

In your armpits and feet (arguably where the strongest odor subsides), you'll find more anaerobic bacteria - bacteria that prefers low oxygen environments and sometimes, higher temperature, humid environments. Because they don't use oxygen to metabolize, their by-products in making energy are often organic acids, commonly lactic acid. Some anaerobic bacterias even have by-products containing sulfur.

Meanwhile, in less warm and damp environments on your body (i.e. face, hands), aerobic bacteria dominate. Oxygen is abundant and the temperature is just right for those strains of bacteria. Their by-products are much less putrid

EDIT: In addition, apocrine sweat is also high in the nutrients, such as lipids and proteins that bacteria can feed on. Once they metabolize the stuff in apocrine sweat, they start releasing the aforementioned by-products.

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  • $\begingroup$ From what I understand from your answer, (1) aerobic vs. anaerobic explains why armpits and feet have the strongest odor, and (2) the variety of odors comes from the variety of bacteria. Could you please expand or add a link about how diverse are the bacteria across different micro-environments? $\endgroup$ – Sparkler May 25 '17 at 23:20
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    $\begingroup$ @Sparkler Here's a link to a good paper that explains the 3 different micro-environments found on skin and the bacteria flora that resides: ncbi.nlm.nih.gov/pmc/articles/PMC2805064 As shown in the paper, there are 3 types of environments. Sebaceous (oily), dry and moist. Here's an excerpt from a book that gives some examples of bacteria found in skin flora: ncbi.nlm.nih.gov/books/NBK7617/#_A512_ $\endgroup$ – PreMedHopeful May 26 '17 at 0:24

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