This is the first thing you should do after you dog has licked, mouthed or bitten a frog or toad. Even if you didn't clearly see what kind of amphibian it was and don't know if it was poisonous, start rinsing immediately. The proper way to do this is to stand behind your dog so you can get a strong grip on his jaw, and force his mouth open while using a hose to rinse it out from the side. It's important to only rinse from the side so you're not forcing any water or potential poison down his throat or windpipe. You should continue rinsing for 5-10 minutes to make sure you have gotten most of the foul taste and/or poison out of his mouth.
2. Wipe your dog's mouth with a clean, wet towel
This is to ensure that you have completely cleaned out his entire mouth. Make sure you wipe down his tongue, teeth, the roof and sides of his mouth.
If your dog did come in contact with a poisonous frog or toad, you don't want to have left any toxins on your dog's body where he can lick it off later. Even ingesting poison this way can kill a dog.
4. Call or visit your vet immediately
Call or visit your vet and describe your situation, and even describe or bring the offending frog or toad if possible. Your dog will receive better and more accurate treatment if your vet knows exactly what the situation is.
5. Give your dog plenty of water to drink
After an unpleasant encounter with a frog or toad, your dog probably won't feel like drinking or eating. However, most dogs who have been poisoned will most likely feel nauseated and will vomit a few times, which will dehydrate them. Make sure he has access to water, which will help him replenish any lost fluids and flush out the toxins in his system.
When my dog mouthed an unidentified frog during an evening walk outside, it was a terrifying experience. He immediately spit out the frog (which hopped merrily away) as if he had tasted something horrible, and began uncontrollably foaming at the mouth. Fortunately, we were near our home, so my dog was immediately rushed to the bathroom where his mouth was rinsed and wiped until there was no foam left. The vet was alerted, and we were told to continue to monitor the dog's situation.
He seemed all right for awhile, if a bit traumatized, then he began to vomit. Over the course of two hours he vomited four times, each puddle of bile significantly smaller than the previous one. It was also difficult to tell whether he was so exhausted because he was possibly poisoned, or if it was just all the vomiting that was taking a lot out of him. He did however, manage to drink a little water, which was encouraging.
Thankfully, after three hours, my dog seemed to spring back to life, and actually approached his bowl hoping to get a little food. He was most likely hungry since he had thrown up his entire dinner onto the floor. He was given a little food and some treats and he very happily ate it all without throwing anything back up. Then he went to sleep. Phew.
We were very lucky that my dog's harrowing experience was not a fatal one, although I still don't know whether the frog he encountered was poisonous or not. However, the above instructions are ones that every owner should keep in mind just in case their dogs are ever bested by a frog or toad.