I think Tylenol is paracetamol, not aspirin? We call it something different down under. The interesting thing about salicylates is that they are the plants natural pesticides, designed to stop pests devouring them and disesases killing them, which is why they are more concentrated in unripe fruit, because the plant doesn't want anyone eating the flesh and distributing the seeds before they are mature. Cunning, huh. (peeling the fruit will significantly reduce the salicylate level.) So technically, salicylates are a chemical. It might not be relevant to your situation at all. I'm just learning about it myself at the moment. Aparently methyl salicylate, which is wintergreen oil, found in mouthwash, etc is added to some pesticides to mask the whiffy smell many of these chemicals have. http://en.wikipedia.org/wiki/Methyl_salicylate My latest theory is that maybe this triggers a salicylate sensitivity in MCS people, like myself, who have had significant pesticide exposure. And salicylates are commonly found in perfumes etc, and the other nasties that cause problems for those with MCS. I'm still doing lots of research...wading through, when the murky brain fog lifts briefly...which isn't very often... Re your sister being autistic, there is a lot of evidence suggesting that people with autism have trouble with sulfites, and that there is a genetic component. A friend who has a major sulfite problem, has an autistic child. His other child also has a sulfite sensitivity. Lots of interesting info here; http://www.enzymestuff.com/epsomsalts.htm Some techinical info here; http://www.newtreatments.org/fromweb/sulfur.html All you can do is experiment on yourself, I guess. And if you don't already, keep a very detailed food diary, so you can try and spot any patterns forming. One simple thing that might be worth a shot, if you haven't tried it already, is to buy a couple of unripe organic peaches and eat them, to see if you get the same jaw pain. If you do, it might be the salicylates. Unfortunately, organic veggies and fruits have more salicylates than the sprayed stuff, as organic farmers tend to use naturally disease resistant plants. But organic stuff has less, or no added sulfites. Still natural sulfur though... Oh the irony... Hang in there... Oh, and my friend with the sulfite problem has one very noticeable symptom when he eats something with sulfites. About 20 to 40 mins later, his face and ears turn red. Do you ever get this? Might be more noticeable with higher concentrations, like those found in dried fruit and wine.