I have had very good results with Rescue Remedy from Bach's essences ( you can find it at any natural/health food store) and composure treats. The treats are natural and safe for both dogs and cats. I got mine from a local vet, but they're available on line in liquid and chew form. Every dog that stays with me gets a composure with a couple of drops of rescue remedy on it. Thundershirts are also a good tool to have on hand when your guest dog is freaking out.