Epiduo and Epiduo Forte are both approved to treat acne. But during the first few weeks of treatment, they may actually worsen your acne. This occurrence is called skin purging, and it can occur with many acne treatments.[1]https://www.medicalnewstoday.com/articles/epiduo#skin-purging
In general, a topical that contains benzoyl peroxide, like Epiduo Forte starts to work after 4 to 6 weeks. Efficacy is based on the severity of your acne, the way you apply the gel/cream, and other factors such as your diet. If there is still no improvement after 3 months of use, you need to advise a dermatologist.[2]https://www.mdacne.com/questions/how-long-does-it-take-epiduo-forte-to-start-working