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Skunk Spray and Dogs
The chemistry of skunk spray

If dog is our best friend, dog’s worst friend has to the striped skunk, a.k.a. Mephitis mephitis(from the Latin word meaning “stench”). It’s only natural that our pooches would be interested in a critter that goes by the name of “polecat,” but woe to those who get too close—a single encounter can leave them stinking to high heaven. Fortunately, there’s a good recipe for a deskunking potion (see sidebar).

But what’s the chemistry of skunk spray—why does it smell so bad, how is it deactivated and, more importantly, does it pose a danger to dogs?

Skunks are armed with dual scent glands, one on either side of the anus, that can deliver a defensive shot of malodorous organic chemicals powerful enough to repel a bear. The pungent odor, which can be described as a mix of rotten eggs and burning tires, comes from volatile hydrophobic compounds containing sulfur called thiols, mostly E-2-butene-1-thiol and 3-methyl-1-butanethiol.

The effective deskunking mixture contains hydrogen peroxide, a strong oxidizing agent that will react with the thiol (SH), remove electrons and add oxygen atoms to generate an odor-free sulfonic acid (SHO3). Baking soda is included to buffer the acid, and detergent helps remove the hydrophobic, oily sulfonic acids. This mix is relatively mild but must be kept out of the dog’s eyes, ears and mouth. (If your dog takes a direct hit to the eyes, veterinarian Rebecca Burwell, DACVO, of Eye Care for Animals in Santa Rosa, Calif., recommends the use of an artificial-tear solution or eye wash to flush out the eyes, and a visit to the vet if they become red, squinty or develop a discharge.)

Fortunately for the canine victim, the volume of spray is small and permanent injury is rare, although there have been reports of serious consequences, and even death, if exposure is severe. The thiols in skunk spray can remove an electron from the iron atom in hemoglobin, resulting in an anemia that causes lethargy, black feces and brown urine. According to Mary Thrall, professor of veterinary medicine at Colorado State University, “Life-threatening anemia doesn’t happen very often, but owners should be aware of this possibility, and have their animal checked following a direct spray.”


Dennis O. Clegg, PhD, is professor and chair of molecular, cellular and developmental biology at UC Santa Barbara.

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