"RAIN ROT" I am glad to hear your equine vet was not pressuring you towards anti-fungal creams, powders or, worse yet, oral medications for the "rain rot" condition of the skin.
If it is indeed a fungal infection, I would recommend TOPICAL APPLICATIONS OF AN HERBAL SOLUTION for helping with pain, itching and the sharp shooting tingles horses sometimes get from a skin break. This will also speed the short term healing, lessen the chance of secondary bacterial infections as well as prevent unsightly hair follicle damage. Anything good for RINGWORM will work for rain rot. Again, avoid harsh chemicals even if they are herbal. I would eschew gooey ointments and salves as well and go with something like OXXY-PHYTE BALM that Jerry Brunetti sells (Agri-Dynamics 610-250-9280). Keep this stuff handy in the barn and stable. You will have good results with HOMEOPATHY as well. More importantly, I would consider a HOLISTIC approach and delve into the reason the immune system is letting invaders into the skin. Minor infections are like the "early warning" signal that something can be wrong on a deeper level. If you are not giving a VITAMIN-MINERAL MIX supplement be sure to do so. Also look at the FATTY ACID intake of the feed. Check for MOLD in the hay or grain as well. Make sure your horses can find pasture/woodland WEEDS for self-worming. How is your well water (mercury, lead, arsenic, PCBs)? Avoid the insane plethora of VACCINES being foisted onto horses these days. Over-vaccination is the root of most immune problems these days. Best wishes, WGW