http://www.sensory-processing-disorder.com/
As you've already seen, SPD can be seen in many different facets....
Some may be SEEKING more input... thus they may be the hyperactive child seeking more input from their surroundings.... they may want spicier foods, or more textures, or things like that..... they may be the ones humming or singing to themselves, seeking more sound input....
Or they may be ones that are overwhelmed with too MUCH input... much like your son and the overwhelming smells he was trying to deal with. They may be the ones that have a lot of oral sensory issues, and have a very self-limited diet... they may be the ones that are driven crazy by certain textures.....
Try to get an evaluation with a specialist..... we could see a lot of issues with our grandson, and once they got the evaluation, that qualified him for OT, PT, and speech therapy......
His SPD isn't THAT overwhelming, but we do see where it interferes with his life.... he doesn't like loud noises, and the hand dryers in bathrooms (and the exhaust fans, too) really scare him..... he will almost refuse to use the toilet in a public bathroom if it is too noisy in there. He does get used to them, though.
We have seen a BIG improvement on several areas since he started therapy 8 months ago...... it has also given his M. tips and ideas on how to work with him and around the issues.
As far as food issues, my grandson will eat almost anything... he even ate Kimchee! However, all of a sudden, he has decided he doesn't like pizza... what kid doesn't like pizza? He usually loves spicy/sour foods, and used to eat raw onion. However, he doesn't like food to be too hot..... he wants us to put it in the freezer to cool it down.
And yes, ADD often co-exists with SPD......