Originally Posted by mom2pride
^ Yeah, that...
However, that said, if he is sweating in a weird pattern somewhere, he may have some sore spots, or something, causing him to sweat more in particular spots, rather than evenly. However, as long as he seems to be performing the same, and isn't 'off' at all, he is probably just reacting to the extra heat, and humidity...tis the season!
Ditto all that. I have one horse with an injured sacrum that, even at liberty in the pasture, if he's not feeling well will sweat profusely from the top of his rump all the way down.
I have another one that I rescued who has an old vertebra injury. His entire hindquarters will sweat profusely (including underneath) at liberty when he is stressed and needs an adjustment. Soon as the chiro adjusts him, the sweating goes away.