Requests for advice for treatment of animal ailments and injuries always make for interesting reading. The obligatory, (and probably sensible), cries of "Call your vet", the helpful old faithful treatments, and often a rather amusing and alarming array of bizarre suggestions always ensue.
What often concerns me is that often when advice is offered it is incomplete, or fails to warn of possible side effects, either from standard use, or over-use when no quantities or regularity of treatment are included in the instructions. At least with a product you purchase through your vet you get clear instructions for use, and a run down of posibble side effects to look out for.
Things like udder cream are unlikely to do any harm, and certainly may do some good, but other commonly used and recomended products and substances can be quite harmful.
Copper sulphate, and zinc sulphate, while both effective in the treatment of things like dermatophilus congolensis infection, being mudfever/greasy heel/rain scald, (same organism, different locations), are also corrosive skin and eye irritants, so suggesting someone "mix a bit of copper sulphate" in with their filtabac or whatever, may result in a cure, but also may result in serious skin durns and damage.
Nappisan also gets a fair bit of support for the same skin problems, but again, this is a product that states clearly to flush skin exposed to it, and while the active ingredient sodium percarbonate is actually quite useful, in my opinion it's medicinal value in the Nappisan product is very limited, if not non-existent, because of the scent and detergent ingredients the product also contains.
Problems also occur as a result of lack of information from those asking for advice. If your horses leg is swollen, then the advice given for swelling coupled with cut, puncture, or broken skin will differ greatly from that where skin is intact.
Some products while great for strain injuries, are extremely painful if used over wounds, and/or broken skin, and gross swelling with broken skin is likely to indicate infection, which most home remedies will not be able to deal with.
Realistically there IS NO real susbtitute for consulting a vet, or at least someone experienced with the animal in question IN PERSON, and when requesting advice from laypeople online you need to know enough to sort the wheat from the chaff when reading through the suggestions given, otherwise you may very find yourself with a vet bill larger than the one you were originally trying to avoid!