Classification of acne The classification of acne reflects the severity of acne and the nature of the lesions, so the treatment of acne should be based on its classification and the selection of appropriate therapeutic drugs and tools. Whether acne is graded according to the International Modified Classification, which is based on the number of lesions, or the Acne Classification, which emphasizes the nature of the lesions, the treatment options are basically the same. Of course, the treatment plan for acne is not set in stone and should be flexible according to the actual situation of the patient, fully reflecting the principle of individualized treatment. Grade 1: Topical treatment is generally used. If only acne is present, topical vitamin A acid preparations are the best choice. Some medical skin care products that have the effects of exfoliating, dissolving acne, inhibiting sebum secretion, and antibacterial can also be used as an adjunctive treatment. Grade 2: Treatment for grade 1 acne is usually used, but oral antibiotics may be used for those with more inflammatory papules and pustules and where topical treatment is not effective. This type of acne can also be treated with combination therapy, such as oral antibiotics combined with topical retinoic acid preparations, or combined application of physical therapy such as blue light, photodynamic therapy, and fruit acid therapy. Grade 3: These patients often require a combination therapy approach, in which the systematic use of antibiotics is one of their basic treatments, and an adequate course of treatment should be ensured. The most frequently used combination therapy is oral antibiotics combined with topical retinoic acid preparations, and also topical peroxymethylphenidate can be used at the same time. Hormonal therapy has also been used with good results in female patients requiring contraception or with other gynecologic indications. Other combination therapies described in this guideline can also be used, such as red and blue light and photodynamic therapy, but attention should be paid to the interactions and contraindications between tetracyclines and isotretinoin drugs, as well as the development of photosensitivity. Those with poor results can be treated with oral isotretinoin alone or with concomitant topical peroxynivalenol. For those who need more than 3 months of systemic antibiotic application, it is necessary to combine such antibacterial agents that do not cause bacterial resistance as peroxymethylphenidate to prevent and reduce the development of drug resistance. Grade 4: Oral isotretinoin is the most effective treatment for this group of patients and can be used as first-line therapy. For patients with more inflammatory papules and pustules, a combination of systemic antibiotics combined with peroxynivalenol can also be applied first, and then switched to oral isotretinoin for lesions such as cysts and nodules after the lesions have improved significantly. The methods used for Grade 3 acne described above and the combination treatments described in this guideline may also be tried. Regardless of the grade of acne, it is important to maintain treatment once symptoms have improved.