Why trust this review
I am Dr. Emily Rhodes, DVM, and I have spent 14 years in equine practice. A large part of my week is advising owners on the unglamorous side of horse keeping: feed, hoof care, stable management, and the constant summer battle against biting flies. Fly control is not a cosmetic issue. Stable flies, horse flies, and mosquitoes drive horses to stamp, kick, and bolt, and they spread disease. So when I evaluate a fly spray, I am thinking about welfare and safety first, and convenience second.
I bought my test bottles at retail. I have no relationship with Absorbine or W. F. Young, and the company did not see this review before publication. For broad horse health guidance I point owners to the American Association of Equine Practitioners (AAEP) and the American Veterinary Medical Association (AVMA), both linked in the sources block below.
How I tested Absorbine UltraShield EX Fly Spray for Horses
I used UltraShield EX over 5 months across a working summer, from late spring into early fall, on a mixed group I see regularly: a 1,150-lb Quarter Horse gelding in daily ranch work, a sensitive-skinned Thoroughbred mare off the track, a gray Andalusian whose light coat shows every residue, and a stocky Haflinger pony on full-day turnout.
I applied it as directed, spraying the body and using a cloth for the face and around the eyes, never spraying directly at the head. I tracked how long horses stayed visibly comfortable, whether flies returned after sweat and after a summer shower, how the coat felt and looked, and whether any horse reacted to the scent or showed skin sensitivity. I noted the active ingredients off the label: 0.50% permethrin, 0.10% pyrethrins, and 1.0% piperonyl butoxide, EPA Reg. No. 1543-15.
Who should buy, who should skip
Buy this if you keep horses turned out in heat and humidity, or in heavy fly pressure near water or livestock, and you are tired of water-based sprays sweating off by noon. The weatherproof formula is its real advantage. It is a strong choice for hard-working ranch and trail horses, broodmares on pasture, and any barn fighting stable flies and mosquitoes.
Skip it, or proceed with real caution, if you have cats in or around the barn, because permethrin is dangerous to them. Skip it for foals under 12 weeks. And think twice if you show light grays or are very particular about coat shine, because the oily film holds dust. For those barns a lighter water-based or wipe-on formula may suit better day to day.
Sweat and weather resistance: where this spray earns its keep
This is the trait that separates UltraShield EX from the budget crowd. On my Quarter Horse, who works up a genuine lather, water-based sprays were useless by early afternoon. The EX formula held visible repellency through a sweaty morning and even through a brief late-day shower on the Haflinger. Absorbine markets up to 17 days of control. I would not bank on two full weeks on a sweating, turned-out horse, but the resistance to sweat and rain is the best I saw against my comparison sprays.
Repellent range: strong against the biters that matter
Coverage is broad. Across the test the horses saw clear relief from stable flies, house flies, and mosquitoes, which are the ones that torment horses near water and manure. The piperonyl butoxide acts as a synergist to boost the insecticides. On the worst horse-fly days no spray is a force field, and these large flies still made passes, but stamping and tail-swishing dropped noticeably versus untreated baseline on the same horses.
Coat feel and residue: the honest trade-off
Here is my main complaint. The weatherproofing that makes it last also leaves an oily film. On my dark Quarter Horse it was invisible, but on the gray Andalusian it grabbed arena dust and dulled the coat by evening. That is the chemistry doing its job, not a defect, but it is a real consideration for show barns and light-colored horses. A quick curry and a rinse on bath day cleared it.
Safety and labeling: read before you spray
I will not soft-pedal this. UltraShield EX is an EPA-registered pesticide containing permethrin and pyrethrins, not an inert grooming product. The label clears it for horses, ponies, foals over 12 weeks, and dogs. It is not for cats. Permethrin is highly toxic to felines, and the ASPCA Animal Poison Control Center lists it among the more common causes of cat poisoning, so a barn cat rubbing on a freshly sprayed horse is a genuine hazard. Keep cats away from treated horses and overspray until it dries. Apply with gloves, in a ventilated space, avoiding eyes, muzzle, and any open wound. I always patch test a sensitive horse first. My Thoroughbred mare tolerated it after a clean patch test, but the strong scent made her fidget on the first application.
For any pregnant mare, very young foal, or horse with skin disease or a history of reactions, talk to your own veterinarian before use and follow the EPA label exactly. Nothing here replaces label directions or a hands-on exam. General horse-care context is available through the AAEP and the AVMA.
Measurements that matter
The numbers I keep coming back to: 0.50% permethrin paired with 0.10% pyrethrins and a 1.0% piperonyl butoxide synergist, under EPA Reg. No. 1543-15. The manufacturer claims up to 17 days. The label age floor is 12 weeks for foals. In practice I reapplied every 1 to 3 days on sweating, hard-worked horses rather than chasing the label maximum, and that gave me the most consistent comfort. The 32-oz bottle covered my four-horse rotation for several weeks of regular use, which lands it at fair value for a weatherproof formula.
If you decide it fits your barn, you can Check current Amazon price.
How this product has changed
UltraShield EX has stayed consistent in its core formula, built around permethrin, pyrethrins, and piperonyl butoxide with the weatherproof, sweat-resistant positioning that defines the EX line within the broader UltraShield family. Absorbine offers other versions in that family, including lighter and green-label options, so confirm you are buying the EX residual formula and not a sibling product if weather resistance is what you are after. I will update this review with the dateModified above if the active ingredients, EPA registration, or label age and species restrictions change. For now, after 5 months of hard summer use, it remains my top pick for sweat resistance, with the residue and the cat safety caveat firmly in mind.