21 CFR § 346.18 - Astringent active ingredients.
The active ingredient of the product consists of any of the following when used within the concentration range established for each ingredient:
(a) Calamine, within a concentration range of 5 to 25 percent by weight per dosage unit (based on the zinc oxide content of calamine).
(b) Witch hazel, 10 to 50 percent.
(c) Zinc oxide, within a concentration range of 5 to 25 percent by weight per dosage unit.