Cats can have a very small lick of vanilla ice cream occasionally without serious health effects, but vanilla ice cream is not a healthy or recommended treat for cats. Most cats are lactose intolerant, so even small amounts of ice cream can cause digestive upset such as vomiting, diarrhea, cramps, and gas. Vanilla ice cream also contains sugar, fat, and sometimes artificial sweeteners that are not good for cats and can lead to obesity, diabetes, and other long-term health problems. Additionally, some ice creams may contain toxic ingredients like chocolate or xylitol which are dangerous for cats. It is best to avoid feeding cats vanilla ice cream and instead provide cat-safe treats or specially made cat-friendly ice cream if a cold treat is desired. Occasional licks from an empty bowl might be harmless, but regular feeding should be avoided.