Yes — peppermints are a proper horse treat
Peppermints have been handed out at stable doors for generations, and for good reason: plain peppermint candies are safe for horses, and the strong mint flavour makes them a high-value reward in a horse's eyes. A single sweet after a good schooling session, or one produced from a pocket to catch a horse who would rather keep grazing, is exactly what this treat is for. The candy is essentially sugar with flavouring, so its place in the diet is as an occasional extra scattered across the week, never as an ingredient in the bucket. Treat peppermints the way you would any sweet in the feed room — welcomed, enjoyed, and finished after one or two.
The sugar arithmetic behind the treat tin
What makes peppermints worth a moment's thought is concentration. The sugar in one or two sweets is trivial beside a day's grazing, but treats rarely stop where the owner intends. A livery-yard fence line, visiting children, and a treat pouch refilled by a kind neighbour can turn a small indulgence into a steady sugar drip for exactly the horses who least need it: the good doers, the cresty native ponies, and the ones whose grazing you already restrict. Hand sweets over one at a time on a flat palm so each is crunched properly, rather than tipping several into a feed where a greedy horse inhales them whole with the first mouthful. A hard round candy swallowed unchewed helps nobody, and a horse who learns to snatch at fingers for mints needs the flat-palm rule most of all.
Choosing from the sweet jar
The plain striped peppermints and simple mint candies sold for people are the standard choice. Sugar-free versions suit horses whose sugar intake you watch carefully, but read the wrapper before the packet joins the treat tin: any ingredient you do not recognise is a reason to choose a plainer sweet instead, and the first sweet from a new brand is best offered on its own, with the rest of the day in which to notice any change in droppings, appetite or behaviour before it becomes the regular reward. A crushed peppermint folded through a small feed is also an old yard trick for persuading a fussy horse to eat something he has decided to inspect suspiciously — a trick to use occasionally, not a daily dressing, or the plain feed will start being refused without it.
When to leave the lid on
Some horses should skip hard sweets altogether. A horse with worn or sore teeth cannot crunch a boiled candy comfortably, and a horse on an active weight-loss plan earns his rewards better as a scratch, a groom, or a handful of soaked hay. Treats of any kind also stop the moment a horse seems unlike himself — off his feed, restless, passing loose droppings — and a change like that after a treat-heavy day is worth reporting to your vet rather than solving by switching brands of mint. For the ordinary healthy horse, though, the rule can stay cheerfully simple: peppermints allowed, two at most, always counted. That is precisely the sort of small rule that gets forgotten between helpers, which is why setting it down in KinsLe's Care Teams, where the people who feed and handle your horse can see his treat allowance beside the rest of his care details, keeps the peppermint policy exactly where you left it.