Pollen Puff's effect varies depending on the target. If it targets an opponent, it deals damage. If it targets an ally, it restores up to 50% of the target's maximum HP. Opponents and allies with Bulletproof are immune to Pollen Puff.
Pokémon affected by Heal Block cannot target allies with Pollen Puff (but they can target an opponent); if only the ally is affected by Heal Block but the user is not, Pollen Puff can target it, but will fail to heal it.