our son has these too. He has some behind his ears. it almost looks like dirt. He gets it in his ear too. I try and try to wipe it away but it doesn't come off. then tonight I noticed he had it under both armpits as well. he does have skin issues but hasn't had any in awhile other then very dry skin. he doesn't seem bothered by it. I tried putting lotion on it tonight. i think we will need a trip to the derm. again. he hasn't been to one since he was 1. he will be 4 in June.
That sounds like what my son gets. This is going to sound gross but it, at least for my son, is basically sweat. My son is the most sweaty child you have ever met (though he seems to be outgrowing it) and will get those brown patches behind his ears, around his ankles, the inside of his elbows, his armpits - places the sweat 'pools.' Behind his ears is the worst.
It isn't that he isn't bathing, but for him washing with a wash cloth isn't enough, especially during hot weather. He needs to be scrubbed with a shower scrubie or such, particularly in those areas. Both to get rid of the spots and also to keep them from coming back.
I have a friend and her son who sweat like my son (like dripping wet if it is over 70 degrees) and they both get them too during the summer.
