Why is my horse all foamy when he sweats?
A few notes to dispel a common myth about horses - a foamy horse is not indicative of a horse that is overworked. The foam on your sweaty horse is the result of the ingredients of your horse’s sweat - and it’s a pretty snazzy horse adaptation. So - let’s talk about latherin.
Latherin is the substance in horse sweat that creates the foam that you see on your horse. Technical: Latherin is a protein that’s also a non glycosylated surfactant. 37% of latherin is hydrophobic. Translated: Latherin is a protein that acts like soap. It’s slippery, and 37% of latherin contains ingredients that repel water.
Latherin is also found in your horse’s saliva, and it’s suggested that saliva is the original source of latherin. Latherin in the saliva helps your horse chew and digest dry forage. Over time, theory has is that latherin became a part of horse sweat to facilitate evaporative cooling with a hairy coat.
This doesn't mean the horse is overworked. It means there is sweat and friction.
When your horse sweats, he is cooled as the sweat evaporates. But, his hair coat (even in summer) is a physical barrier and traps the sweat. So, latherin acts to slickify the sweat so that evaporative cooling is effective. And yes, I did just type slickify. It’s not a word - yet… The foam is produced when the soapy properties of latherin are rubbed. Just as your sponge will foam up as you start to wash the dishes, the same is true for your horse. Reins and butt cheeks and girths will foam up the sweat. You will tend to notice it more where there is friction involved.
Some horses get super soapy and foamy, others do not. Again, it’s not a sign that your horse is overworked. It’s actually a really good sign - and you know that when you see latherin your horse’s own cooling system is working. Now don’t panic if you have never seen it on your horse - that doesn’t mean your horse’s sweating system is “broken”, it very likely means that there’s not friction on the sweat. However, if your horse doesn’t sweat at all, or only partially sweats, you may have a horse with anhidrosis or partial anhidrosis. This is an entirely different scenario that needs careful management and Veterinary care.
A teeny, tiny patch of latherin induced foam.
Does your horse get foamy when he sweats?