Whats the best treatment for nettle stings?

My little boy has just fallen into some stingy nettles! he's 17 months old. The stings are all over his arms, back and all up the inside of his legs. (he was in the paddling pool so he only had trunks on) its obvioulsey irritating him coz he's screaming. whats the best way to cool the swelling and stop the itching?