People need to be really really careful with sodium hydroxide. It burns, and it keeps burning even after extensive irrigation. It (does something like) binds to fat, which makes it really hard to irrigate. Sodium Hydroxide burns probably require skin grafts to heal properly. So, yeah, go careful with it.

I say all this because I know someone who used to self-harm with sodium hydroxide and I've seen the results and treatment (in a variety of English hospitals specialising in burns) first hand.