Urtica dioica, where is your sting?

Or rather - Stinging Nettle, who is your sting for? My little dog does not seem bothered by stinging nettles, even when emptying her bladder rather clumsily all over them. Which makes me wonder if stinging nettles are able to sting animals - perhaps fur and feathers are a protection. Have stinging nettles evolved especially for us naked apes?