Our friend 'cured' her dog of petroleum toxicity here. A van had crashed into the stream just above the house and leaked gasoline. The dog, a Tennessee Walker (a hound dog by any other name), had gotten into the stream shortly after the crash.

Ma, the dog, became listless and weak. She laid around with a glazed look on her face. Our friend fed her some charcoal capsules. The next day, Ma was still out of it. Our friend was attracted to the labyrinth that I'd just mowed in our front yard. She took Ma up and walked her in and out. Ma seemed a little better. She walked her in and out twice more. Ma began to perk up. By the end of the last walk she was frisky, biting at her leash and jumping around. Miraculously, Ma was her old, frisky self. 

Not exactly a quantitative, double blind test, but it's the only story I've got about pet healing in the labyrinth.