Our group operates under the assumption that every ability that deals negative energy damage Heals undead creatures, which makes a lot of sense considering how many places contain an entry like:
Since undead are powered by negative energy, this spell cures them of a like amount of damage, rather than harming them.
Is the opposite of this also true? Are living creatures affected by Positive Energy Healed instead of Harmed?
While "[i]n general, positive energy heals the living and hurts undead creatures" (Player's Handbook 311), some rare positive energy effects that deal damage don't also heal the living.
For example, the 6th-level cleric spell bolt of glory [evoc] (Spell Compendium 35-5) launches a "white bolt of hissing positive energy" that only deals damage, and the 5th-level psion/wilder power celestial conduit [psychokinesis] (Complete Psionic 80) brings forth a "massive charge of positive energy from your psyche into the material world" that also only deals damage (although the effect does deal even more damage to undead creatures).
It's best to adjudicate whether a positive energy effect that deals damage also cures damage based on the spell's description rather than making that in general a constant.
To a certain extent, yes.
Positive energy heals living creatures and damages undead. However, too much of a good thing is bad, even in DnD situations.
This excerpt from the Positive energy plane reads:
This power is dangerous to mortal forms, which are not made to handle it. Despite the beneficial effects of the plane, it is one of the most hostile of the Inner Planes. An unprotected character on this plane swells with power as positive energy is force-fed into her. Then, her mortal frame unable to contain that power, she immolates as if she were a small planet caught at the edge of a supernova.
