Rain rot or rain scald, is a skin infection and you should get a specified lotion or cream either from a vet or from a feed merchant that sells these products.
To prevent it, always make sure your horse is thoroughly dry before rugging him up and regularly check and if necessary remove his rugs a few times a day to prevent sweating as the bacteria flourish in warm damp environments. If he is wet, dry him off with either towels or put on an anti-sweat cooler and walk him round. Also make sure your rugs are dry too before putting them on. If he is in the stable and is sweating up remove a rug or switch to a lighter rug.
Re: Rainrot on his back
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