Whenever I go out dancing, my hair usually ends up saturated in sweat from all of the high-intensity activity. I've noticed that this makes it fuller once it dries, even into the next day before I shower. So why not just skip the shampoo altogether the day after and rinse with water only? I've tried that the past two times I've gone out, and it looks a lot better than when I shampoo out all of that oil and sweat. Apparently I'm not the only one who's hit on this idea, although it is marketed as "beach hair" rather than "sweaty hair."
But as you can see from this recipe, they add not just sea salt to water but some kind of essential oil too. Sure, you get salt from going to the beach, but not oil -- unless there's been a spill or something. Water, salt, and oil -- that's what your skin is pumping out when you reach a high level of physical intensity. As far as hair goes, our minds evolved to prefer signals of health and vigor, not the flat-against-the-scalp signals of inactivity or of only low-intensity exertion that would characterize the sick, the poorly fed, and the elderly. (Do sprinters have better hair than marathoners?)
As with other aspects of human appearance, fashion often works against what is truly attractive. You don't even have to look through National Geographic with its exotic tribes whose women scar up their flesh to show group membership. Like fashion in clothing, the new look for girls in the '90s and 2000s was minimalist, razorslim hair. One of my former tutorees, brimming over with excitement about making herself up and how intimidating it would look, said that then we're gonna go straighten our hair -- like Mean Girls straighttt.
It seems like this fashion cycle is particularly long, as the '60s through the '80s all had comparatively voluminous hairstyles for both men and women. (Wild times call for wild hair.) The adoption of polyester probably helped out with the sweaty hair look during the '70s. Similarly, for the past two decades it's mostly been the super-straight and tightly manicured look that's been in for men and women. Hopefully the recent obsession with beach hair is more than a passing fad, something that hints at a coming return to wildness in the culture. There are always bad examples of any fashionable look, but if you look at how high the peaks are, for my money the '60s - '80s hair looked the best. They don't make 'em like Jean Shrimpton or Kelly Kapowski anymore.