In the past month or so as it has warmed up my horse has been getting really flakey skin mostly on his neck and upper legs. I think it's from sweat, bugs, etc. I try to rinse him off after every ride to keep sweat from building up and do lots of currying. Is there anything else I can do?
Whatever the convergence of elements, you'd do well to help the skin be less vulnerable. I only know of one source that actually adds in oils and nutrients to strengthen skin WHILE killing any irritants. Usually things used for cleaning and skin problems actually ultimately parch the skin, leaving it more vulnerable. Hence, feeding the cycle. There is an easier and more cost effective paradigm. A truly all-in-one shampoo changes the game: http://www.luckybraids.com/troubleshooting.pdf
I agree with the others that say it's the fly spray - I posted the same type of question last summer. I was using the same spray (Tri-Tech) I had in the past with no issues, and all of a sudden my horse had this flaky black skin funk (neck and chest mostly) that wouldn't stay away. I quit using fly spray completely for about a week, started back with a different brand, and haven't had an issue since.
"And I saw heaven opened, and behold a white horse..." ~Revelation 19:11