There are several effects and items that deal damage to the user and have the language "This damage cannot be reduced or prevented in any way". For example the Bloodclaw Weapon in Adventurer's Vault.
I know that means that damage reduction wouldn't apply. And that you couldn't let another party member (such as a paladin) step in and take that damage for you.
Does that text affect the healing of that damage in any way?
Is there any reason I couldn't regenerate or second wind to recover those hit points?