[header] How to calm a cat [title] Think of your and your cat's safety first. [step] Only approach the cat if it is necessary to do so, such as a trip to the vet. The majority of agitated cats benefit from being left in peace, rather than being petted or picked up. 
If you do have to approach the cat, the very first thing you need to do when your cat is upset is to protect yourself and then the cat. Scared or aroused cats can and will bite their owners and they will scratch.