Ask which of three depths a peel is meant to reach before you agree to it. The depth sets how much skin injury you are signing up for.
The three depths
DermNet says peels may result in superficial, moderate depth or deep skin injury.
What DermNet names for the deeper two
For the medium depth peel, DermNet says trichloroacetic acid (TCA) is the most common chemical used. For the deep peel, DermNet says phenol results in deep skin injury.
Papers on specific peel agents
DermNet's page on chemical peels is the longer read behind these lines. For specific agents, see the PMC paper on chemical peeling agents in melasma and the PMC paper on a professional-grade TCA-lactic acid chemical peel for photoaging and hyperpigmentation for more depth.
Questions for the provider about depth
Ask the provider to name the chemical, the depth, and the healing plan in one sentence each. If they cannot, wait.