Since liniment basically does nothing more than provide some very superficial cooling (repeat, VERY superficial) and make the horse smell good, the most cost-effective solution is to stop using it altogether. If you want the area to be cooler, use ice or cold hosing. If you want to soothe sore muscles and don't want to use cold therapy, give a massage and/or use standing wraps. Rubbing alcohol is a good lubricant for equine massage and is dirt cheap.
Some people argue that certain liniments with arnica and/or witch hazel in them, like Sore No More, do something. It's true that arnica does provide some surface numbing, sort of like Icy Hot, but there's a big diff between numbing a sensation and actually healing the soreness.
I do make my own "liniment" to use when sponging off though. I use one large bottle of Listerine (generic works just fine - and any color... I like the wintergreen), one bottle of witch hazel and a bottle of rubbing alcohol. Mix together and then I repour it back into the orginial bottles... using as needed. I've also sprayed it on. Not sure if it helps (probably doesn't) but it smells good and seems to help get the coat a bit cleaner.
I mix my own as well. General recipe is equal parts alcohol, witch hazel, and cider vinegar. Sometimes I add some store bought to the mix. Sometimes I just alcohol and witch hazel to the store bought to stretch it. I've also mixed in a tub of dollar store blue gel-type liniment to make the mix a little thicker. My favorite store bought is Vetrolin.
Any linament that smells good, produces no allergic reaction to you or the horse and is cheap is best. It is a massage medium, and not much more. The old leg men on the track are testament to the fact it is the massage, not the lubricant, that does the job - many of them used plain water and that was what was left on the leg from the cold water therapy or a bath.
Here's one of mine: 1 Imp Qt (40 oz) cider vinegar, same of water. 1/2C each salt and epsom salts, 8 oz witch hazel, and 'flavouring' - enough wintergreen, eucalyptus, or something to make the whole lot smell more like linament and less like pickle juice. Heat the water and disolve the salt, cool to luke warm, add the remaining liquids.
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