I have a best to any vet’s knowledge sweet itch/insect bite hypersensitivity horse. The best thing to do for him is to keep him covered! Face, body, and legs. My horse itches his face and legs the worse, and is actually very self inflicting if allowed.
Have not come across much luck with antihistamines thus far…still trialing a few. The horse does respond to steroids but is borderline metabolic and aging so we need to use those sparingly.
I’m actually doing decently knock on wood at keeping him semi comfortable right now. He gets his itchies washed 1-2x a week with Microtek medicated shampoo and an oatmeal shampoo. I SLATHER him 6-7 days a week with neem oil (life saver!) and desitin (diaper rash cream) on anything super open that can’t be covered with fly gear. I also like to use cortisone cream on the face.
Seriously though look into neem oil. Many sweet itch people use this over in the UK.