“How much Benadryl can I give my horse?” Veterinarians hear this often from concerned owners of horses with hives or other allergic reactions. The owners go in the Internet and see that Benadryl helped another horse. Actually, it’s the active ingredient, diphenhydramine, that helped — not specifically the brand name Benadryl. Dosage depends on how much the horse weighs and what allergy it is being treated for.
Methods of Administration
Do not give human Benadryl pills or tablets but veterinary diphenhydramine to a horse, unless using Benadryl lotion. Diphenhydramine is the active ingredient in Benadryl and is given to quell some allergic reactions, especially to allergic reactions to insect bites or nettle rash. In these cases, diphenhydramine may be used in shampoos, topical sprays or lotions.
In cases where diphenhydramine is given to horses as a countermeasure for drug allergies such as for the performance enhancing drug fluphenazine, the dosage is usually given intravenously, according to Current Therapy in Equine Medicine (Elsevier Health Sciences; 2009.) How much Benadryl does a horse get then? It’s a bit higher at 1 to 1.5 milligrams per kilogram that the horse weighs.
If a horse is allergic to a blood transfusion and suddenly breaks out in hives, it may need an intravenous injection of 0.5 milligram per kilogram that the horse weighs, according to AAEVT’s Equine Manual for Veterinary Technicians (John Wiley and Sons; 2009.)
Treatment for Sweet Itch
Sweet itch is the common name for a horse that breaks out in itchy hives due to the bites of Culicoides gnats. Benadryl Itch-Stopping Gel sold over the counter for people is one home remedy for this irritating problem. But a horse is so large and a bottle of Benadryl Itch-Stopping Gel is very small.
Dr. Matthew Mackay-Smith recommends making a horse-sized lotion using Benadryl Itch-Stopping Gel as one ingredient. Blend together:
- 4 to 8 ounces Avon Skin So Soft
- 4 ounces Benadryl Itch Stopping Gel
- 8 ounces Aveeno Anti-Itch Concentrated Lotion
- 8 ounces Gold Bond Medicated Body Lotion Extra Strength
Apply to the sores or hives twice a day. Also, try placing a fly sheet on the horse to prevent bites and feed two teaspoons of garlic to help make the horse not taste so appealing to the gnats.
Diphenhydramaine can make a horse drowsy. How drowsy? Diphenhydramine is a banned substance in some horse sports such as all equestrian events in the Olympic Games. One German equine athlete in the Athens 2004 Summer Games, Ringwood Cockatoo, had a diphenhydramine lotion placed on him to treat hives on his back. Traces of this showed up in his urine during a random drug test. They did not medal in the three day event but were cautioned.
Sources
Reeder, Deborah, et al. AAEVT’s Equine Manual for Veterinary Technicians. John Wiley and Sons; 2009.
Robinson, Norman Edward, et al. Current Therapy in Equine Medicine. Elsevier Health Sciences; 2009.
Mackay-Smith, Matthew, Dr. “Treating Sweet Itch.” Equus Magazine. Cruz Bay Publishing, Inc.; June; 2000.
FEI Press Release Dec. 4, 2004. http://www.thehorse.com/ViewArticle.aspx?ID=5299
