[ The expression makes him look younger and isn't unattractive in the least. Hellboy finds himself feeling glad to see it and lifts a shoulder in a shrug as he offers the little bottle back across the table. ]

Call it a professional interest. Though most of the stuff I keep around is because of what it keeps away, not what it heals. Holy relics and things like that. Fought off some guys with just a silver button once, that was pretty interesting.