Preparation H is not recommended for dogs. While a small lick of the ointment is unlikely to cause a life-threatening emergency, the product contains ingredients that can harm dogs through both ingestion and topical absorption. The risks depend on which formulation you have, how much your dog was exposed to, and whether they ate it or it was applied to their skin.
Why Preparation H Is Risky for Dogs
Preparation H comes in several formulations, and each one contains at least one ingredient that poses problems for dogs. The standard ointment contains 0.25% phenylephrine hydrochloride (2.5 mg per gram), a drug that constricts blood vessels to reduce swelling. In dogs, phenylephrine stimulates receptors that raise blood pressure and can trigger dangerous heart rhythm changes. Even topical application of phenylephrine in dogs has been shown to elevate blood pressure and slow the heart rate through a reflex response.
Other Preparation H products contain hydrocortisone, a steroid that penetrates canine skin more readily than you might expect. Research on canine skin has found that certain surface conditions can more than double the rate at which hydrocortisone passes through the skin barrier. If applied to irritated or broken skin, absorption increases further. Repeated topical steroid exposure in dogs can thin the skin and, over time, contribute to hormonal imbalances.
Some formulations also contain zinc oxide. The Merck Veterinary Manual classifies zinc oxide ointments and creams as a low toxicity risk for acute ingestion, meaning a single exposure typically causes nothing worse than vomiting and diarrhea. The more serious form of zinc poisoning, which destroys red blood cells, comes from swallowing metallic zinc objects like coins or hardware, not from licking a cream. Still, repeated ingestion of zinc oxide products isn’t something you want to allow.
What Happens If a Dog Eats Preparation H
Data from 89 dogs that ingested hemorrhoid preparations paints a fairly consistent picture. Vomiting was the most common symptom by far, occurring in 84% of cases. About 9% showed lethargy, 6% developed diarrhea, and a smaller number experienced heart rate abnormalities (either too fast or too slow) or trembling. Two dogs developed high blood pressure, with one recording a systolic reading of 210 mm Hg, which is dangerously elevated for a dog.
Ingestion of hydrocortisone-containing creams can also irritate the stomach lining. In dogs, this occasionally progresses to ulcers or bloody vomit and dark, tarry stools. The risk scales with the amount consumed, so a small dog eating a full tube faces a very different situation than a large dog that got one lick.
If your dog ate Preparation H, the most important details to note are: the specific product name, the size of the tube, roughly how much was consumed, and your dog’s weight. This information helps a veterinarian or poison control line assess the actual risk. Most cases resolve with monitoring and supportive care, but cardiovascular symptoms like an abnormally slow heart rate or visible tremors warrant urgent attention.
Topical Use on Dogs
Some pet owners consider applying Preparation H to a dog’s irritated anal area, reasoning that if it works for human hemorrhoids, it should work for a sore rear end. The problem is twofold. First, dogs will almost certainly lick the area, turning a topical application into an ingestion. Second, the ingredients aren’t formulated for canine skin or canine conditions.
Dogs with anal irritation usually have a different underlying issue than humans with hemorrhoids. The most common culprits are impacted or infected anal glands, allergies causing perianal inflammation, or bacterial skin infections. Preparation H doesn’t address any of these causes. Applying it may temporarily reduce visible swelling, but it masks symptoms while the actual problem worsens.
What Veterinarians Use Instead
For anal gland problems and perianal inflammation, veterinary treatment follows a different approach entirely. The standard procedure involves flushing the affected anal sacs with sterile saline, then infusing a combination ointment that contains an antibiotic, an anti-inflammatory steroid, and an antifungal agent. This targets infection and inflammation simultaneously, which a single-ingredient human product cannot do.
Treatment is typically repeated at two-week intervals until symptoms resolve. This protocol was effective in a study of 33 dogs with anal gland inflammation, where the combination of flushing and medicated ointment addressed both the bacterial component and the swelling.
For simple skin irritation around the rear end that isn’t related to the anal glands, veterinarians may recommend a pet-safe topical. Hydrocortisone cream (plain, without the other Preparation H ingredients) is sometimes considered safe for short-term use on dogs’ dry or itchy skin when used under veterinary guidance, but the concentration, duration, and location all matter. Applying any steroid near a mucous membrane or on broken skin changes the absorption profile significantly.
The Bottom Line on Safety
A single small exposure to Preparation H, whether licked off skin or nibbled from a tube, is unlikely to be fatal for most dogs. But “unlikely to kill” is a low bar for safety. The phenylephrine in the standard ointment can raise blood pressure and disrupt heart rhythm. The hydrocortisone in other formulations absorbs through canine skin faster than expected and causes GI problems if swallowed. And any formulation applied near a dog’s rear end is virtually guaranteed to be licked off and ingested.
If your dog has anal irritation, swelling, or scooting, the fix isn’t in your medicine cabinet. These symptoms almost always point to an anal gland issue or an infection that needs proper diagnosis and targeted treatment.