Does cornstarch help a diper rash?

No.

Using cornstarch can be dangerous. There could be bacteria in the cornstarch that enters open pores in irritated skin and multiply under the diaper.

Instead, use an over-the-counter zinc oxide product (for example Desitin, Balmex and Butt paste and Sudocrem ) with every diaper change to help heal diaper rash and protect your babys bottom from further irritation while rashes heal . Be sure diaper change regularly and allow air-dry time