The frustrating thing about anhidrosis is they've yet to determine what causes it (although there are some theories and some serious possibilities that are being looked at), no cure for it and everyone has some treatment for it that worked with horse A, C, D and H, but did nothing with horse B, E, F or G. At least that what the claims are.
It can come in varying degrees of severity. The only thing that is known to work with all horses is just keeping them cool (shade, fans, standing in a pond or stream up to their stomach in the water and under the shade of a tree, hosing them down, mist sprayers, air conditioning, etc....). You can keep them cool without any additional expense. My older mare had a bad case of it one Summer after a relocation and I just kept her in a shaded area most of the time and let her play in the pond a lot. The next year she was sweating, but it took two years before she was back to normal. I know one girl who must have gone through several cases of Guinness one Summer trying to get her horse to sweat. He still didn't sweat that Summer, but he developed a real taste for Guinness
. Of course she loves to say it was what caused him to eventually start sweating when Summer was over, but he was sweating before Summer started
. He did sweat better the following year so he didn't get a season worth of Guinness again (I guess it wasn't too bright