Explosion protection
What changes
Ipecac still fires explosive projectiles. Pyromaniac prevents explosion damage and can refill red-heart health when an explosion reaches Isaac.
How to approach the setup
Check your character's available health before relying on the healing. The protection is useful even when there is no red-heart health to refill.
A practical suggestion for this pair. Check the rest of your inventory and the room before relying on it.
The caution to remember
It does not generate soul, black or eternal hearts. Enemy contact and ordinary projectiles can still hurt you; this pair is not general invulnerability.
What this teaches about a run
Protection against one damage source can solve a weapon's main drawback without solving every danger in a room.