Why is my beautiful horse doing this to himself??

Recently Cinny has started rubbing himself....baaaaad. I am not sure what is going on here and I can't figure it out. First he did it to his neck but then he stopped and I have been putting MTG on it and the hair is now growing back.



But now he is rubbing his butt bad...not his tail, that is still fine, just his butt so whatever he is rubbing on he is flipping his tail over it. At least I THINK he is rubbing. It started in small patches on each cheek and yesterday covered a good 2"X4" area on each one. This morning I get there and it's now down his legs. I can't see anything except what looks like very very dry skin and what is getting to be an area that looks and feels the texture of beef jerky. Sorry, didn't think to take the pics until after I put MTG on it.







I walked the fence line and can not find any signs of him rubbing except maybe a broken off branch in an evergreen tree and there is a really old wood support in a corner that looks like it's taken some recent damage...not chewed but the wood definitely looks recently damaged. We scraped some of the dandruff off and looked at it with a high power magnifier and it just still looks like skin. Nothing creepy crawly movin around.

He has been at my friend/trainers house for a month. He is in a pasture with just Brom that he can eat to his hearts content and I make sure he has fresh water daily. My friend told me today that she thinks there might be some St. Johns Wart in there somewhere but she has never know it to cause this. Before he was moved to this pasture he was in a dry lot with a round bale that was predominantly Brom.

This started before I EVER bathed him myself so I don't think it's shampoos or anything. Bathing doesn't seem to help. I did stop using RepelX on him because he started shortly after I started using RepelX. I gave him a good bath and put nothing on him and he seemed okay for a day or so and then the rubbing started up again.

Has anyone seen this before? Does anyone have even a guess at what it could be?

I would guess that maybe he is suffering from some sort of skin allergy, possibly brought on from something in his environment that he has never encountered before or maybe it is a newly developed allergy (and it could be anything from a certain plant to common grass). I think that vets can test for allergies in horses, you might consider having that done.

Is he up-to-date on deworming? What was the last kind of dewormer, and do you rotate types?
Is he in a paddock/pasture with any possibly harmful plants?

He had Zimectrin Gold the last week of April that his previous owner gave him before I took possession of him. She says she rotates dewormers for her horses regularly. He started the rub on his neck about a week after moving him to my friend's. Then he stopped rubbing the neck and is now rubbing the bum.

The only plants in his pasture are some evergreen trees, free growing brome, and a little st. Johns wart. He is moving to the local Equestrian Center a week from Tuesday, unless they won't let him in because of his skin. There he will be back on dry lot with a round bale and companion horses. He has one companion horse now. We put her in thinking he started rubbing because he was used to being with 7 other horses and now he's alone.

Maybe it's the evergreens, he likes to stand with his bum in them. I also found out today there is a small amount of St. Johns Wart, so my friend says, but I have yet to find it.

It definitely appears to be an allergy...especially if it just started this spring; there are alot of allergins this time of year (and fall), and one never knows when a horse will acquire an allergy.

What I would do, is have the vet do a skin scraping on it, and make sure that all it is is an allergy; rule out fungus' and other infection related things. Then treat accordingly.

I would probably also put something like Aloe Heal, or even Hydrocortisone on it for the time being, as either will keep the places moist, and help reduce itching and swelling (due to irritation)...maybe even wash those areas with a mild shampoo or soap, as that will help remove the allergins, and help cleanse the areas and keep them from getting infection.

Oh, wow. I didn't know that could have that kind of effect on animals. We don't have it around here. It is possible that's the problem.

Do you mean the evergreens or the st. Johns wart? I have never heard of St. Johns Wart doing it but I know it can cause other issues, but evergreens...I have never put horses with them before either, but I do know that the type she has is an oilier type so maybe he's getting the evergreen oils/sap on his bum and it's itching him.

mom2pride made an excellent post. It might be a fungal thing. I was thinking possibly worms, but usually they itch higher (dock area) - still might be something to check on if the skin scraping comes back negative?
I'm thinking allergies too.

I meant the St. Johns Wort (though we don't have many evergreens either LOL). I found this website with some info on it.
St John's wort