A dog foaming at the mouth and convulsing all over may be poisoning, epilepsy, canine distemper, rabies, toxoplasmosis, etc. The dog needs to be sent to the pet hospital for examination immediately to avoid life danger. You should pay attention to your dog's diet, don't feed your dog random food, and deworm and vaccinate your dog on time to avoid contracting diseases. You should wear a leash when going out to prevent your dog from accidentally eating rat poison.