I just had this happen to my four yr old. I looked on the internet and it says that titanium oxide (?) Is what you should get if kids have a reaction and that anything with ---benezone will cause the reaction. (please don't take this as gospel because it didn't come from a dr just google) I had put Neutragena (I forget which formula) on my daughter and her arms cheeks, and neck are all rashy and itchy. I haven't gone yet to the store to see if i can find somethign that has the oxide in it.
for what it is worth, Chris may have something there with the chlorine being the irritant, someone on the message board that i found the info about the ingredients mentioned that she didn't react to the sunscreen itself, but the combination of sunscreen and water (probably the chlorine) resulted in a rash.
IF i can find somethign that works for my dd, i'll edit this response or message you, and please do the same if you find something before i do.
Another tip, is that the "surfer" type swimsuits with the longsleeves block the UV rays, check the tag to be sure. that way your son is exposed to less chemicals. Don't solve the ears and nose but it might be an idea.