Sweat/ protein rash?

[Horse*]

Hello, my horse has a rash mainly on the left side of his neck, first noticed it when he was clipped about a week before Christmas. Whilst it hasn't got any worse it also hasn't gone away so wondering if there is anything I can do to help it on its way or just let it run its course?

Not sure whether it is sweat rash or protein, IMO more likely sweat but is there any way of deciding it just from its appearance?

 

[Horse*]

anyone?!

 

[JillA]

In my experience a reaction to protein takes the form of urticaria (lumps under the skin) and ususally clear up pretty quickly once the body adjusts to the change in diet. Is that the case or is it more of a broken skin type rash? In which case yu might need to become a detective try and work out what allergen he came into contact with at the time it bega. Sweat rash is usually only in warm damp confined areas like between legs or in armpits?