if you crush it to a fine powder, be careful not to inhale - as it can cause adverse effects such as nose bleeds. no matter how careful i am in weighing this stuff out it will fly into the air.
i use salicylic acid (the main ingredient in aspirin) in one of the prescriptions i make in the pharmacy for a dermatologist - guess what it's for. chemical peel. but there are other active ingredients in it. again, i use a face mask when i compound with this stuff - we purchase the bottles in powder form so no need to crush it - and it's pure salicylic acid. aspirin tablets will have other inert fillers in it. but that doesn't matter in this case.
enteric coated aspirin - it's just coated so that it doesn't start getting digested in the stomach - the coat stays on until the tablet gets to your intestines then the coat and the pill begins to dissolves. so if you are using this for your face, save yourself the money and buy the uncoated stuff. enteric coated aspirin is for people who's stomach are sensitive to aspirin (easily irritated).
and yes, aspirin is not recommended for under age 18 years because it can lead to Reyes syndrome.....but i believe that's in the case of ingesting it. there are topical agents - Clearasil, Neutrogena, OxyClean - that contain salicylic acid, so to me it sounds ok to use the crushed aspirin topically. the only thing would be in terms of concentration and i can't give you that answer since it depends on how many tabs you use.
hth!
oh, i forgot to mention - don't do this too much, with too highly concentrated aspirin mask and leave it on too long - salicylic acid is also used to remove some warts and corns (just go look at Dr. Scholl products - it's salicylic acid at a higher concentration)
