Chlorhexidine scrub. You don’t even need to rinse it off…for my broodmares in the field far from a hose, I apply a bit of chlorhex scrub (usually in morning when legs are wet from dew), work into a lather, trying to get the gel into scabby bits but NO PICKING. Apply once or twice daily, scabs should clear up within a week depending on severity. I like to use a syringe to apply, especially an old “Tomorrow” syringe with the fine pointed tip.
In my experience treating bacterial as fungal, or vice versa results in the scratches/mud fever getting dramatically worse very quickly.
Iodine based scrubs and zinc work well on bacterial mud fever.
Antifungals work well on fungal forms.
Sometimes you get lucky (Not!) and one will allow the other to get a foothold.
My younger horse used to have every scratch below hocks and knees go fungal before it healed. Eventually he developed a case that crawled around his leg leaving healed patches behind, but always moving into new areas. Vitamin E supplementation made a huge difference to him, and now lower legs scratches usually heal normally, barring unusual circumstances.
So, how can you tell which you’ve got? The cases I have had here were quite distinctive. Bacterial scratches formed thick, red/brown, crusty scabs that tend to crack and ooze yellow/orange serum. When the scab was knocked off the wound would ooze bloody serum.
Fungal scratches, in the early stages, and after a scrub clean with an iodine scrub, had thin, flat, off white, soft “scabs”. Those scabs would go black, grow thicker, and crack apart, looking like a bunch of tightly packed miniature pine cones standing on their ends. When knocked off, the wound bled freely without serum.
Fungal forms should be kept dry, with washing limited (my vet recommended once a week, max) and dirt brushes/wiped off prior to treatment application. If the environment is wet I use zinc ointment over my antifungal to keep the moisture away from the skin.
Bacterial forms often respond well to daily iodine scrubs, allowing the scrub to sit on the site for a while before rinsing, then after drying off a thick layer of zinc ointment. Be aware that warm water washing is an invitation for the bacteria to move into new places as the warm water opens up the skin pores. Iodine scrubs tends to be very drying to skin, which can also create new places for the bacteria to take hold. The zinc ointment provides a moisture barrier, but it also soothes dry skin.
Scratches/mud fever suck in large part because there are so many infective causes, environmental factors, and different treatments.
Good luck with yours!
Theoretically, but only if you know exactly what toxin you’re looking for, in which case you’d have to know what plant your horse is likely eating. So it still comes down to knowing what’s in your pasture.
Dr. Deb Bennett wrote a really comprehensive book on plants poisonous to horses, with pictures and all kinds of info on how to identify, symptoms of toxicity, etc. You can Google it and find her book for purchase. Even if your horse’s issue does turn out to be an authentic dermatitis, it’s still an amazing resource to have.
