Rescue Remedy is natural flower essences that comes in a bottle. You drop some in their water and it is supposed to have a calming effect. It has calmed down some of my fosters in the past. I am not too sure it would work for Oliver though.

Here's a little about it from a website:

Rescue Remedy is made from Impatiens, Clematis, Rock Rose, Cherry Plum and Star of Bethlehem. It remedies stress, distress, tension, and restores calm, reassurance and relaxation.