The present invention relates to the preparation of compositions comprising benzoyl peroxide, with or without other additional active ingredients. The process involves introducing benzoyl peroxide, along with any other active ingredients present, into a fatty substance that contains and protects the ingredients that would otherwise be unstable when in contact with one another. The composition is designed to allow all ingredients to become available for skin contact or skin absorption when the fatty substance softens and/or melts as the composition is applied to the skin. The benzoyl peroxide may be pre-micronized to a particle distribution size of about d90 of 0.1 to 150 microns, preferably d90 of 10 to 15 microns. Further, pharmaceutical or cosmetic ingredients may be contained within the fatty substances, with or without, benzoyl peroxide therein or may be present outside of the fatty substance but elsewhere within formulated pharmaceutical or cosmetic products using the active ingredients protected by the fatty substance. These compositions are useful in aqueous-based formulations to treat diseases by topical, transdermal and/or subcutaneous administration.
