Background Although pre-emptive therapy with oral tetracycline, moisturizer, sunscreen, and topical corticosteroid is useful for preventing acneiform eruption (AfE) due to epidermal growth factor receptor (EGFR) inhibitors, no studies have examined the efficacy of topical corticosteroids themselves, or investigated the optimal potency of corticosteroid for treating facial AfE (FAfE). Patients and methods Screened patients with RAS wild-type colorectal cancer started pre-emptive therapy with oral minocycline and moisturizer on initiation of cetuximab or panitumumab therapy. Patients who developed grade 1 or 2 FAfE were randomly allocated to two groups: a ranking-down (RD) group that started with a very strong corticosteroid and serially ranked down every 2 weeks unless FAfE exacerbated; and a ranking-up (RU) group that started with a weak corticosteroid and serially ranked up at exacerbation. FAfE grade, patient quality of life, and adverse events (AEs) with topical corticosteroid were evaluated every 2 weeks. The primary endpoint was the total number of times grade 2 or higher FAfE was identified in the central review of the 8-week treatment period. Results No significant differences in total numbers of grade 2 or higher FAfE or in AEs caused by topical corticosteroids were observed between groups during the 8 weeks. Incidence of grade 2 or higher FAfE tended to be lower in the RD group during the first 2 weeks. Conclusion Considering the long-term care of FAfE, the RU regimen appears suitable and should be considered the standard treatment for FAfE due to EGFR inhibitor therapy. Trial registration UMIN Clinical Trials Registry (UMIN000024113).