Why Some People Cannot Sweat
If you've ever been in a situation in which you're so nervous, or hot, or both that you sweat right through your clothing (and who among us hasn't?), the inability to sweat might (at first) sound almost ideal. People who can't perspire, however, have their own very specific challenges with which they must cope, including risk of heatstroke.
Per Business Insider, a small number of people have a rare disorder called anhidrosis, which renders their bodies incapable of producing sweat. Most people with anhidriosis can't perspire because their sweat glands are damaged from either trauma or genetic conditions that impede the glands' development.
In 2014, researchers from Japan's RIKEN Brain Science Institute and Uppsala University in Sweden studied a Pakistani family in which five children couldn't sweat. Scientists found nothing wrong with any of the children's sweat glands, so after analyzing the family's genomes, they determined that the children's anhidrosis was caused by a genetic mutation. The mutation was in the ITPR2 gene, which controls a basic cellular process in sweat glands.
The connection between calcium and sweat glands
Upon the publication of their study in the Journal of Clinical Investigation, the researchers put out a press release, posted at Eureka Alert!, in which they explained that the ITPR2 gene encodes IP3 receptor type 2 (or IP3R2), a protein that typically forms within a cell and releases calcium, which then triggers essential cell behaviors such as secretion. Dr. Katsuhiko Mikoshiba of the RIKEN Brain Science Institute noted that this study discovered the first known example of "IP3 receptor type 2 mutation in human disease."
The scientists were further surprised upon learning that the gene mutation is a "point mutation," which happens when a single "letter" within a person's genetic code changes, as opposed to a larger deletion of genetic materials, which can cause more dangerous or extreme mutations.
Blonde hair in some Solomon Islanders and some Europeans is another genetic quirk proven to be caused by two different point deletions that differ according to where the blonde's ancestors are from.
As for anhidrosis, Dr. Niklas Dahl of Uppsala University pointed out that it's actually quite rare, particularly compared to its " 'opposite' phenotype, excess sweating or hyperhidrosis," which affects up to two percent of the general population.