Maybe your armpit stains aren't just because of the warmer summer weather: they may be encoded in your genes.
Sweating is a critical component of how we regulate our body temperature, but unfortunately, sweating a lot isn't often portrayed as an "attractive" quality. In fact, some people have hyperhidrosis (a clinical diagnosis for excessive sweating), which may even be tied to a difference in cardiovascular stress response compared to the average person.
In a new study, two new loci were found to be related to excessive sweating. One of the loci was at a region that has previously been related to sweating in general, while the other is located near genes that may be involved in determining whether your earwax is wet or dry, as well as your body odor. Here's the link to this interesting study: https://www.ncbi.nlm.nih.gov/pubmed/29895819
Check Genomelink to find out to what extent you are genetically predisposed to excessive sweating!