To kill fleas and ticks on dogs, mix 1.28 fluid ounces of permethrin 10% concentrate per gallon of water. That’s a 1:99 dilution ratio, producing a final concentration of 0.10% permethrin. This is the standard label rate for direct application on dogs, and getting it right matters because the concentrate is potent enough to cause serious problems if used too strong.
Complete Dilution Chart
Permethrin 10% concentrate can be mixed at several ratios depending on the intended use. For dogs, only one ratio applies, but the full chart helps you understand the range and avoid mistakes.
- 1:99 (dogs, fleas and ticks): 1.28 fl oz concentrate per gallon of water, yielding 0.10% permethrin
- 1:199 (premises/yard spray): 0.64 fl oz per gallon, yielding 0.05%
- 1:399 (light pest control): 0.32 fl oz per gallon, yielding 0.025%
- 1:39 (not for dogs): 3.2 fl oz per gallon, yielding 0.25%
- 1:19 (not for dogs): 6.4 fl oz per gallon, yielding 0.50%
The only ratio labeled for direct use on dogs is 1:99. The stronger concentrations (1:19 and 1:39) are intended for treating surfaces, fabrics, or livestock premises, not your dog’s coat.
Measuring Without a Graduated Cylinder
Most people don’t have lab equipment in their kitchen. Here’s how 1.28 fluid ounces translates to common measurements: it’s roughly 2.5 tablespoons, or about 7.5 teaspoons. If you have a standard medicine cup marked in ounces, fill it just past the 1-ounce line.
For smaller batches, scale down proportionally. A half-gallon needs about 0.64 fl oz (roughly 1.25 tablespoons). A quart needs about 0.32 fl oz (just under 2 teaspoons). Precision matters here. Eyeballing with a “splash” of concentrate is how dogs end up overexposed. Use a measuring syringe or kitchen measuring spoons and measure carefully.
How to Apply the Mixture
Once mixed, the solution is used as a spray or dip. For a spray, pour the diluted mixture into a spray bottle and mist your dog’s coat thoroughly, working the solution down to the skin. For a dip, sponge or pour the solution over the dog’s body, saturating the coat. Either way, avoid the eyes, nose, and mouth. You don’t need to rinse afterward. Let the coat air dry completely, which allows the permethrin to bind to the hair and skin where it continues killing parasites on contact.
Most dogs tolerate the 0.10% concentration without any issues. You can reapply as needed for ongoing flea and tick control, but follow the intervals specified on your particular product’s label, typically no more than once every seven to fourteen days.
Signs of Overexposure in Dogs
Even though permethrin has a wide safety margin in dogs at the correct dilution, mistakes happen. Using too much concentrate, applying it undiluted, or a dog licking a large amount of the solution can lead to toxicity. Watch for excessive drooling, vomiting, tremors, hyperexcitability, weakness, or difficulty breathing. There is no specific antidote for permethrin poisoning. Treatment is supportive, meaning a veterinarian manages the symptoms (controlling tremors, preventing dehydration) while the dog’s body processes the chemical.
If your dog shows any of these signs after application, wash the remaining solution off with mild soap and water immediately, then contact a veterinarian or animal poison control.
Permethrin Is Lethal to Cats
This is the single most important safety point with permethrin products. Cats lack a liver enzyme (glucuronide transferase) that dogs and humans use to break down permethrin. Even trace amounts transferred from a recently treated dog can cause fatal poisoning in a cat. Spot-on products designed for dogs contain permethrin concentrations of 45% to 65%, and these kill cats. But even the diluted 0.10% spray can be dangerous to a feline in the household.
If you have cats, keep them completely separated from any treated dog until the dog’s coat is fully dry. Better yet, consider a different flea and tick product entirely. Permethrin poisoning in cats causes severe neurological symptoms, including tremors and seizures, and it can be fatal even with aggressive veterinary treatment.
Getting the Math Right for Your Batch Size
Most people don’t need a full gallon of solution for one dog. Here’s a quick reference scaled to common batch sizes at the 1:99 (0.10%) ratio for dogs:
- 1 gallon (128 oz water): add 1.28 fl oz concentrate
- 1/2 gallon (64 oz water): add 0.64 fl oz (about 1.25 tablespoons)
- 1 quart (32 oz water): add 0.32 fl oz (about 2 teaspoons)
- 1 pint (16 oz water): add 0.16 fl oz (about 1 teaspoon)
A quart is usually enough for a small to medium dog. Large breeds with thick coats may need a half gallon or more to fully saturate the fur. Mix only what you plan to use. While diluted permethrin solution can be stored briefly in a sealed container away from sunlight, fresh batches are more reliable.