Although not specifically a skin condition, this ailment is where the horse is unable to sweat in extreme heat and humidity, and therefore cannot handle a normal working program. It is usually a condition that occurs in tropical climates - particularly if the horse is moved from a cooler climate to a tropical one. However, exactly the same inability to sweat can manifest in temperate weather where it may be less obvious, and even remain undiscovered if the animal is not worked hard.

A horse's fluid and electrolyte balance and his ability to cool through the evaporation of sweat are critical. It is a lot to ask that one adjust from either cold dry or hot dry weather to hot humid overnight. In the first instance - if you are moving a horse between extremes, give him time to acclimatise, or move him during the winter rather than in the heat of summer.

Also, if the horse has been on commercial electrolytes, take him off them long before he is moved to get his kidneys back to working properly so he can cope with the extra demand in the tropical climate. Then put him back on commercial electrolytes and extra salt when he first arrives, and then wean him off again - going back to natural 'electrolytes' . If commercial electrolytes are used judiciously in special cases like this and not given as a routine, all horses would be better off!

Helpful Herbs
The herbs that stimulate the lymphatic system and the sweat glands are Fenugreek and Horsetail. Make up two cups of each up into a tea to be added to the horse's drinking water twice per day, and do this for 6 weeks before moving if there are any suspicions as to the horse's ability to sweat freely whatsoever. Continue the treatment for a further month in the new environment. Preparing Mint tea for your horse and having Mint growing alongside the water trough is another useful diaphoretic tonic that promotes sweating.
Keep Kelp and Sea Salt freely available to the horse and give Rosehips as part of his regular feeding regimen.