What are the tests for erythema toxicum?

None I'm aware of. Erythema toxicum is a transient condition affecting 1/3 to 1/2 of newborns & is relatively easy to diagnose on exam. I don't need a confirmatory test. Microscopic exam of some of the tiny blisters will yield eosinophils, a white cell associated with allergy.It's a cute test but i haven't done one since medical school.