a couple of years ago I mixed up 3 or 4 1000mg L-Arginnie caplets (I removed the shell and poured out the powder) with some water and a little moisturizer (Nutrogena 'visably young') gave it a good ol' shake to mix then procceded to apply to my scalp.
.......
20 seconds later the worst burning sensation had me running (and I mean that literally) to the bathroom in a panic to stick my head under freezing cold running water to wash off my lava concoction !!!!!
that stuff was like hydrchloric acid !!!
no harm done, just a red patch for a few hours, the funny thing is is I rubbed a load of this stuff on my arm there was no burning at all, and obviously you can ingest the stuff with no problems....??
just a warning, but I am sure it can be done correctly, just don't go mixed up an arbitary amount and slapping it on your head.