Acne marks left on the back are also known as post-inflammatory hyperpigmentation, which belongs to the acquired pigmentation abnormality disease, and can be relieved by general treatment, medication, and physical therapy. 1. General treatment: For patients with mild post-inflammatory hyperpigmentation, even if they do not receive treatment, some of them may fade away on their own, so they can be temporarily observed and left untreated. 2. Medication: For the phenomenon of serious localized hyperpigmentation, you can cooperate with your doctor to choose Vitamin A cream to apply, which can promote the renewal of epidermal cells and reduce localized hyperpigmentation. 3. Physical therapy: the commonly used physical therapy for the brush acid treatment, patients can be fruit acid peeling, promote skin metabolism, and then accelerate the fading of pigmentation. For the acne marks left behind, patients should combine their own situation, consult the local regular hospital dermatologist, choose the appropriate treatment, do not blindly use drugs.