cyproheptadine can have a side effect of increased appetite... I use it for my dog when he goes on eating strikes.
i've always heard benadryl and horses is not a safe combo. Wish i had data to back that up
My guy developed a case of hives this past week and the only thing I had on hand was benadryl. The vet said to give one tab (25mg) per body weight, which is about 10-15 tabs depending on your horse. She said they may be a little groggy. The hives kept continuing, and they said it would be better to try the tri-hist for long term....
It sounds as though you are dealing with just one episode, but if it recurs you might get your horse tested for allergies and then go for the desensitization shots. They have really helped my two mares with allergies.
When needed we use Hydroxizine under vet supervision also. Have used Dexamine (compounded, anti-histamine + Dex) for severe bug bite episodes.
i use anihist by animed for my mare's allergies and have found it to be very effective and easy to feed. it does not run the risk of causing anhidrosis like the trihist but does have a 72 hour withdrawal period before competitions! this is the only thing that keeps her from sneezing and rubbing her nose on everything in the spring! and its super cheap!
Had a pony break out in hives that was so bad it looked like bubble wrap under his skin. Dex is not a good option for him and he did not respond at all to Tri-Hist. Vet advised IV banamine and 8-25mg Benadryl every 12 hours until cleared. Worked like a charm and he was hive free in 24 hours. 25mg/100 lbs is the usual dose.
I have an 1100lb tb that has random allergies. One adult bendryl powder capsule broken open and mixed into his food am and pm for a few days works really well for him - then i dial back to one a day to none. Dex doesn't really work for him.
It does make them sleepy.
I also feed Equinacea from Equi-lite and spirulina am and pm (although you said the spirulina didn't do much for your guy).
Had great results for hives and coughing with Hydroxy. Vet said its mild, and has fewer chances of side effects than other options. Did have to go to Prednisolone instead once, but figured out what the allergy was and was able to eliminate it. I asked her for the mildest options and these two were what we used.
Tried Benadryl, but it had no effect on the hives. Had TriHist on hand, vet said go ahead and try, but unlikely to help hives. She was right.
Horse was a bit sleepy shortly after given Hydroxy dose, lasted a few hours tops. I wasn't competing at the time, and just rode long after dosed.
No advice just wishing you good luck. Only experience I have is that we give patients hydroxy when we sedate them so they dont get sinus drainage. Doesnt really help you though. I hope you get it figured out and find something that works.
Member of the ILMD[FN]HP Clique, The Florida Clique, OMGiH I loff my mares, and the Bareback Riders clique!
I had a horse respond well to Hydroxyzine, never had a problem with side effects. The horse was super sensitive- had to use fragrance-free detergent to wash pads, wraps, etc. and it was a battle finding a flyspay that didnt bring out the hives. Hydroxyzine kept the hives under control for the most part. If something triggered a bad outbreak IV Banamine usually did the trick.
Gave Hydroxy twice per day. Same with Prednisolone. Dosages were kept to the lowest amount possible while controlling symptoms.
Horse had some muscle wastage from the Pred. Pred is a Catabolic rather than Anabolic steroid, which is why it is a possible side effect. Horse was on high dose at the time, and it resolved easily as soon as we started reducing the dose. I never did find research on horses in particular on Catabolics, but did see it as a side effect for dogs and humans, and certainly seemed the case for my horse. We chose the Prednisolone because vet felt it had a much lower incident rate of founder as a side effect.