One of my cats came back from a 5 day stay at the vets and his brother, who is usually the most laid back cat, started hissing and striking out at him. After a couple of days of this behaviour I ordered the spray and plug in. Within 15 minutes of using the plug in they had returned to their normal loving behaviour. Will be recommending this to all my friends. Unlike other reviews I found very little odour from the plug in and did not find the spray offensive.