How long does dog poisoning usually take to show?

Onset time varies by cause and the dog’s constitution, generally from a few hours to a day. Spoiled or rotten food causes symptoms in 2-3 hours, while pesticide poisoning acts within half an hour, so the exact time depends on the toxin. Poisoned dogs often show depression, muscle tremors, shivering, and foaming vomit; if you see these, give soapy water or diluted hydrogen peroxide to induce vomiting, then take the dog to a vet promptly.