Harm Spell and Caster

[Ballistic101]

If a caster uses the three action version of the Harm spell, I assume they are also take the damage.

Is there any way to negate this, outside of being a certain ancestries(undead)?

[Salamileg]

Emanation Rules wrote:

An emanation issues forth from each side of your space, extending out to a specified number of feet in all directions. For instance, the bless spell’s emanation radiates 15 or more feet outward from the caster. Because the sides of a creature’s space are the starting point for the emanation, an emanation from a Large or larger creature affects a greater overall area than that of a Medium or smaller creature. Unless the text states otherwise, the creature creating an emanation effect chooses whether the creature at its center is affected.

The caster chooses if they're affected or not.