It looks worse to humans. The cats don't take it personally, so stay calm, and don't communicate your own anxiety to them. Introducing Your New Cat to Other Pets - From the Denver Animal League. Adding a New Animal to the Household - from Cyberpets. Read all 3 parts.
Article includes cat and dog intros.
Signs to be aware of if one of your cats is having difficulty adjusting to a new cat. Rescue Remedy - A good link to understanding Rescue Remedy and the Bach Flower Essences. Rescue Remedy can be obtained at any Health Food Store. Use 4-8 drops twice a day mixed in food, food gravy, water or squirted directly into the mouth. This is homeopathic, so you can't overdose.