Occasionally when I walk my dog I notice him eat stinging nettles!! this freaks me out. Is it ok and why does he do it? Doesn't it sting him? I wonder if others's dogs do this too?
If he eats YOUNG nettles it doesn't sting. Nettles are a great source of iron so probably your dog lacks it.
I don't know if nettles can sting dogs but I'm thinking about camels that are able to chew thorns easily! Perhaps dogs have some kind of protection in their mouth or their saliva neutralizes the stings.

My dog eats stinging nettles almost daily. He seeks them out and they don’t seem to affect him at all,not his nose or tongue. He clearly needs them.

One of my two large dogs eats them and knows exactly where to get them on our walk. He's big at 95lbs but never once has it bothered him. I thought maybe it was to help with arthritis but either way it makes him happy so no harm no foul.