Allergic reaction? On neck.

[Connemara24]

Pony who is on full loan, but will be going back in a month. Since old horse passed away I had to move him up the road to a friend's yard as had no companion, any way now moved him to wear I work just until he goes back, current routine in during day out at night, the day before yesterday he started having a rash very bumpy on his neck/shoulders and yesterday it was worse quite hot and a bit on his bum, doesn't seem itchy. He is bedded on straw and is on hay. I rode him yesterday and he wasn't his usual stressy strong self if anything he was calm/ lethargic. He has been very stressed recently with all the change but has settled now. Any ideas.
Thanks everyone.

 

[AmyMay]

Was he on shavings previously?

 

[Connemara24]

Was he on shavings previously?

No always on straw, thanks

 

[Goldenstar]

At this time of year I find that horses are prone to skin infections .
I would wash him with malaseb according to the the instructions.
Be sure to leave the foam on long enough I do fully twenty minutes .
If that does not clear it you May need oral antibiotics and perhaps steroids .
You will have to get malaseb from the vet take some pictures they may prescribe it without seeing the horse if you email pictures. When the weather is sunny get him standing without a rug in the sun as much as possible .

 

[Birker2020]

Could be anything from a bacterial skin infection to urticaria.
My previous had a bacterial skin infection from going through a water complex at a popular XC course on a fun ride. The water had white foam on top and he had to go on a course of special shampoo from memory.