21 CFR § 358.720 - Permitted combinations of active ingredients.
(a) Combination of active ingredients for the control of dandruff. Salicylic acid identified in § 358.710(a)(4) may be combined with sulfur identified in § 358.710(a)(7) provided each ingredient is present within the established concentration and the product is labeled according to § 358.750.
(b) Combination of control of dandruff and external analgesic active ingredients. Coal tar identified in § 358.710(a)(1) may be used at a concentration of 1.8 percent coal tar solution, on a weight to volume basis, in combination with menthol, 1.5 percent, in a shampoo formulation provided the product is labeled according to § 358.760.