If you're concerned, go see a doctor about it. If you're not having a problem, but just are curious about it, then I probably wouldn't worry too much. When I get back from a long ride my dog can't stop licking me because I am very salty. I can't actually see crystals, but it's there nonetheless. If you sweat more than an average person, I would expect what you are describing. Just make sure you are drinking enough.