Some people see yellow stains on the armpits of clothes, thinking it is sweat, but sweat is not colored . Yellow stains on the armpits of clothes are a sensitive thing. It reminds you that you might get body odor, because One factor in the formation of body odor has emerged, that is, unsaturated fatty acids. The apocrine glands secrete viscous, milky yellow liquid, which is unsaturated fatty acid, which is excreted through sweat, and combines with external streptococci to decompose to form body odor. Therefore, yellow sweat marks are a yellow warning of impending body odor.