Salty skin taste

I would appreciate it if a doctor or someone with specific experience reply. I have a son, 5 years old who I have recently noticed had salty tasting skin. This has been after he had been playing all day, etc. Not after a bath or anything. But it tasted salty sometimes none the less. I don't know if this is normal for the skin to taste salty like this after sweating. He has bad allergies and mild asthma. He had a ENT doc test him for allegies and he came back as being allergic to alot of stuff(e.g., dust, cat hair, roaches, cows, dog hair, pollen, etc). He takes an allergy shot once a week. But he is in the top 95% for his height and weight, and is very healthy otherwise---in fact, his energy level is off the charts. He doesn't have any respiratory problems to speak of, no persistant coughing or wheezing. Please respond. Thanks