What Causes Unusual Sensations In Fingers?

My 9 year old son has been having a strange sensation on the tips of his fingers for the last few years on and off. He describes it as powdery. He breathes into his hands to relieve it and he says it helps but it doesn't go away. He feels it almost every night, when he plays ball he says his fingers feel sticky and he relieves them under water but as soon as he dries them they feel sticky or powdery again. It goes away eventually on its own but now I'm starting to worry because it's been a few years and at the beginning I didn't take him seriously. Please help me with this, what could that be? Libby