Why diarrhea appears a day later
Kerosene doesn't hit the intestines immediately—it first irritates the stomach lining, causing nausea and drooling. By the time it reaches your 15 kg dog's lower gut, the inflammatory response kicks in, drawing water into the intestines. That's why you're seeing watery stool now rather than yesterday.
The diarrhea may contain mucus or have a faint chemical smell—both signs the kerosene has damaged the intestinal lining. Don't use over-the-counter anti-diarrheals—they could trap toxins in his system longer.
The hidden risk in post-exposure drinking
Many dogs try to 'wash out' the kerosene taste by gulping water, which worsens the diarrhea. Excess fluid combines with the inflamed gut to create that characteristic watery consistency. Watch for attempts to drink from puddles or the toilet—it's better to offer ice chips if he's desperate for moisture.
If his stool transitions from watery to bloody or tarry black, that signals deeper ulceration requiring immediate vet care—at 15 kg, he can lose dangerous amounts of fluid quickly.
How body weight changes the danger level
A larger dog like yours has more gut surface area to absorb kerosene toxins, but also more reserves to handle the fluid loss. The real concern is whether he's still absorbing hydrocarbons—press your ear to his belly; if you hear loud gurgles (borborygmi) between diarrheal episodes, the irritation is ongoing.
Weigh him if possible—a 2% body weight loss (300 grams for your dog) from diarrhea warrants vet intervention to prevent shock.
When to expect symptoms to peak
Kerosene-related diarrhea usually worsens over 24-36 hours before gradually improving, assuming no further exposure. But watch for 'improvement' that's actually dehydration setting in—fewer stools but with increased lethargy or dry gums mean he's losing the fluid battle.
Collect a fresh stool sample in a baggie—vets can check it for fat globules (steatorrhea), a sign of intestinal lining damage unique to hydrocarbon ingestions.
The step-by-step response, from the first minute to the vet visit, is in our Kerosene Poisoning in Dogs and Cats emergency guide.