Moved to a new barn in March. Have owned my guy for over 19 years. First time with “rain rot”. Though I’m not 100% sure it’s rain rot. Bumpy tufts of hair on his body. Mostly on rump. One circle area on both sides of upper rib cage. Dandruff (flaky stuff on top of hair) long his neck. cannon bone crud (which we’ve dealt with before so not unusual) I’ve cleaned a lot of it up with grooming, bathing. What’s left on his rump is moist clumpy goopy stuff in tufts of hair. I have no idea how to describe it accurately. I can get a chuck with my finger nails and pull at it. It comes out with hair. But it is not dry. It is not scabby. It’s like moist goop in his hair - causing tufts. I’ve tried blue stuff, equiderma lotion, nothing - leaving it dry for a few days. I’m unclear how to get it out. Manually picking it out irritates him and pulls hair out. But since it’s not dry I can’t get it to come out any other way. Please throw all options at me. Fall weather has settled in so bathing is going to be really hard soon (lack of hot water as well). I feel like a bad mom. I don’t think I curried him enough and the new barn environment has more turnout and also turnout in rain. Old barn did not turn out in rain. So it’s likely my fault unfortunately. But I’m struggling to resolve it. Thanks!
Try washing the infected areas with a shampoo that has both chlorhexidine and miconazole (Malaseb shampoo, for example) or just soak with a dilute betadine solution. For small areas, I sometimes rub Biozide gel on and leave it. Biozide is basically betadine in gel form. It’s used for superficial wounds, but it also works for small areas of rain rot. You’ll probably have to treat several times to eradicate it. If you wash with Malaseb shampoo, be sure to leave it on 10-15 minutes before rinsing. Also, soak your grooming tools in a 10% bleach solution so you won’t keep reinfecting when you groom.
I feel your pain. Both of my horses get rain rot from time to time because they love to stand out in the rain and roll in mud, especially in winter when it’s too cold to bathe them.
Wash infected areas and apply cornstarch to get really dry. Medicated foot powder works as well. Keep him dry and look at his diet if this is a new thing.
My guess would be higher iron in the new place or less vitamin e.
It’s possible there is higher iron. What would I do for that?
So the fact that it’s not scabby but is actually goopy-ish and moist is in fact rain rot? Why then does lotion like equiderma work? If you want to dry this out?
Betadine scrub works very well.
Add copper/zinc to counter balance the iron.
No clue about Equiderma, I’ve never used it on rain rot. I would assume it’s helps the skin heal and protects it.
Wash and keep dry and it generally goes away unless an underlying health issue.
is there a way to know I’m dealing with a iron imbalance?
The easiest way is to get your forage tested, and input the results + your hard feed into something like Feed XL and see how the iron:copper:zinc:manganese ratios shake out.
(edit to remove reference to testing water since iron in water appears to not be readily metabolized by horses, so is more-or-less a non-issue.)
@SmlHpy1, I don’t know whether your horse has rain rot or something else. I only know for sure that my horses get rain rot from time to time. It’s possible that your horse has rain rot, or it could be something else entirely. Or it could be rain rot along with some other secondary infection. The treatments I suggested (shampoo with both chlorhexidine and miconazole or betadine in some form) will treat both bacterial and fungal infections, so they should be good for whatever is wrong with your horse if it’s a superficial skin infection.
Do other horses in your new barn have similar skin problems? Do they share grooming utensils?
In any case, if the suggestions you get here don’t help you might want to ask your vet what to do.
No shared grooming. I guess I was just wondering if the soft, goopy feel is actually rain rot. I just don’t know how to get that out of his hair. I’m not sure it’s even infected skin as it seems to be in the hair and I can get my nails in space between that and the skin. I’ll try betadine of chlorhexidine. Thanks!
Just know that the iron in water is being shown to be fairly unavailable to horses, so not nearly as big a deal for most horses as we’ve been lead to believe.
That said, it’s a fact that most forage in the US (and pretty much the world) tends to be higher in iron, and lower to dramatically low in copper and zinc. It’s not even so much about ratios, which are not defined as necessary by any formal body, other than potentially the cu:zn ratio.
It IS about getting enough minerals in, usually copper and zinc, rarely manganese, and that’s not terribly hard to do.
@SmlHpy1 the goopy nature doesn’t sound like rain rot, but it could be. There are good suggestions for some washes and topicals.
If you’re not sure it’s even at skin level, are you sure it’s not sap? My horses come in these days with some level of sap somewhere, on the spots they are usually scratching, which sometimes includes the top of the rump
Fantastic, one less thing to worry about! I’ll update my post for future readers 
@JB - Ok well my first thought was this barn is on well water and so I thought maybe high in iron.
Oh gosh! I guess it could be sap! I didn’t think about that. That’s interesting. I’m having a friend look at it tonight. I’ll see what she thinks. No matter what it is, I didn’t catch is soon enough . . . so let’s say it is sap and it’s been on him for a while - how the heck do I get that off?!
I’ve had sappy horses, when Cottonwood buds land in the paddock in spring and the horse sleeps on them. Mostly on the belly.
The total picture here in the OP sounds more like a skin issue maybe in different stages. The medicated shampoo and powder route is the way to go and I don’t think there’s any danger in using them too long or even proactively.
Flax in feed really helps with skin and hair.
Lowered immune system can be an early sign of Cushings.
It could be, but it’s more likely the forage is high iron which makes the real issue of low cu and zn.
Sap is “easy” to remove with peanut butter, or cheap vodka 
Then, of course, wash!
If none of these dietary and topical solutions work for you, you might have your horse tested for Cushing’s, just to be on the safe side. This is exactly how my old guy initially presented.
My horse is already being treated for Cushings.
Sometimes rain rot cases need the help of antibiotics. Perhaps this is true for you because a) your horse is immunocompromised due to PPID and b) you mentioned it was cold to bathe.
My mare was having a somewhat similar issue. Suddenly in the late Fall she got these bumpy, small scabby things along her loin area. If I curried or tried to remove them it hurt her. I added a mineral to her RB for several years now and it has never returned.
