Acne is a chronic inflammatory skin disease involving the sebaceous glands, with a prevalence of 70%-87% and a greater psychological and social impact on adolescents than asthma or epilepsy.G. The treatment options for acne vary widely among dermatologists, with some treatments having uncertain efficacy and lacking clinical trials in the literature, and some even causing harm to patients, resulting in a negative social impact and financial loss. Therefore, for clinicians who are currently engaged in clinical dermatology without formal dermatology training, it is essential to have a set of effective treatment guidelines to regulate the treatment of acne.
1. Pathophysiological factors of acne
The occurrence of acne is closely related to many factors such as excessive sebum secretion, follicular sebaceous duct blockage, bacterial infection and inflammatory response. The pathophysiological basis of acne is the rapid development of sebaceous glands and excessive secretion of sebum, and the development of sebaceous glands is directly governed by androgens. After puberty, the level of androgens, especially testosterone, increases rapidly, and testosterone is converted to dihydrotestosterone in the skin by the action of 5-alpha reductase, which binds to androgen receptors in sebaceous cells.
This increase in androgen levels promotes the development of sebaceous glands and the production of large amounts of sebum. Some patients with acne have higher blood levels of testosterone than those without acne. In addition, progesterone and dehydroepiandrosterone in the adrenal cortex also have a pro-sebum effect. Sebum is mainly composed of keratins, wax esters, triacylglycerols, and small amounts of sterols and cholesterol esters.
Abnormal keratinization of the follicular sebaceous ducts is another important factor. The formation of acne begins with the enlargement of the sebaceous follicle, which occurs secondary to abnormal keratinization of the keratinocytes. In the lower part of the follicular funnel, the lamellar granules of keratin-forming cells are reduced and replaced by a large number of tense filaments, bridging granules, and lipid inclusion bodies, which are not easily shed.
The secretion and discharge of large amounts of sebum can easily lead to bacterial infections. Various microorganisms such as Propionibacterium acnes, Staphylococcus albicans and Malassezia are present in the hair follicles, with Propionibacterium acnes infection being the most important. Propionibacterium acnes is an anaerobic bacterium, and the obstruction of sebum excretion creates a good local anaerobic environment for it to proliferate. The lipase produced by Propionibacterium acnes can break down triacylglycerols in sebum to produce free fatty acids, which are the main factors leading to inflammatory damage in acne.
In addition, P. acnes can also produce peptides that chemotactic neutrophils, activate complement and cause leukocytes to release various enzymes, which can induce or aggravate inflammation. In addition to the above factors, the occurrence of acne in some patients is also related to the immune function of the body, especially in some specific types of acne such as acne conglobata and acne fulminans, where the immune response plays an important role.
2.Grading of acne
Acne classification is an important basis for acne treatment and efficacy evaluation.
According to the nature and severity of acne lesions, acne can be classified into three or four grades:
Level 1 (mild): acne only;
Grade 2 (moderate): inflammatory papules in addition to acne;
Grade 3 (moderate): pustules in addition to pimples and inflammatory papules;
Grade 4 (severe): nodules, cysts or scarring in addition to acne, inflammatory papules and pustules.
3.Local treatment of acne
3.1 Localized washing
Wash the face with water to remove the mixture of oil, flakes and bacteria from the skin surface, but do not over-wash. Do not squeeze or scratch the acne with your hands. In addition, do not use oily, fatty, powdered skin care cosmetics, ointments and creams containing glucocorticoids.
3.2 Topical medication
3.2.1 Vitamin A acid drugs
① 0.025%~0.1% retinoic acid (all-trans retinoic acid) cream or gel: This drug can regulate the differentiation of epidermal keratin-forming cells to dissolve and discharge acne. The skin is mildly irritated at the beginning of 5 to 12 days, such as local flushing, flaking, tightness or burning sensation, but it can gradually disappear. Therefore, it should be used from low concentration, applied once a night, avoiding light to increase the irritation of the drug, and applied topically once a week after the symptoms improve.
②13-cis-retinoic acid gel: regulates the differentiation of epidermal keratinocytes and reduces sebum secretion, once or twice a day.
③2nd generation retinoids: 0.1% adapalene gel, once a night, for mild to moderate acne. 0.1% tazarotene cream or gel, once every other night, to reduce local irritation.
3.2.2 Benzoyl peroxide is a peroxide, which can slowly release neo-oxygen and benzoic acid after topical application, with the effect of killing Propionibacterium acnes, dissolving acne and astringent. It can be formulated into 2.5%, 5% and 10% lotions, emulsions or gels, and should be used at low concentrations to start with. A gel containing 5% peroxymethylphenidate and 3% erythromycin can improve the efficacy.
3.2.3 The antibiotics erythromycin, chloramphenicol or clindamycin (clojibromycin) are more effective when prepared with ethanol or propylene glycol at a concentration of 1% to 2%. 1% clindamycin phosphate solution is a water-soluble emulsion free of oil and ethanol for acne patients with dry and sensitive skin. 1% clindamycin solution is also effective.
3.2.4 Azelaic acid can reduce the flora on the skin surface, in the hair follicles and sebaceous glands, and especially has an inhibitory effect on Propionibacterium acnes and acne lysis, which is effective for different types of acne. It can be formulated into a 15%-20% cream for external use, with local erythema and stinging as adverse effects.
3.2.5 Selenium disulfide 2.5% selenium disulfide lotion has the effect of inhibiting fungi, parasites and bacteria, and can reduce the free fatty acid content of the skin. The method of use is to clean the skin, the solution is slightly diluted and evenly spread on the site of seborrhea, about 20 minutes and then wash with water.
3.2.6 Sulfur lotion 5%-10% sulfur lotion can regulate the differentiation of keratinocytes and reduce the free fatty acid content of the skin, and has a certain inhibitory effect on Propionibacterium acnes.
4.Antibiotic treatment of acne
Oral antibiotics are one of the effective methods for treating acne, especially moderate and severe acne. Among the many colonized microorganisms (including Staphylococcus epidermidis, Propionibacterium acnes, Malassezia and other gram-negative bacilli), only live Propionibacterium acnes has a clear association with the aggravation of acne inflammation.
In addition to infection-induced inflammation, immune and non-specific inflammatory responses are also involved in the process of acne inflammatory damage, so antibiotics that both inhibit the propagation of Propionibacterium acnes and have non-specific anti-inflammatory effects should be given priority. The above factors, combined with the pharmacokinetics of antibiotics, especially the selective distribution of seborrheic sites, should be preferred to tetracyclines, followed by macrolides, and other antibiotics such as sulfamethoxazole-methoprene (cotrimoxazole) and metronidazole can also be used as appropriate, but β-lactam antibiotics should not be chosen.
Among the tetracyclines, the 1st generation tetracyclines such as tetracycline are poorly absorbed orally and have low sensitivity to Propionibacterium acnes; the 2nd generation tetracyclines such as minocycline, doxycycline and lymetetracycline should be preferred, and they should not be substituted for each other. The main or commonly used antibiotics for systemic infections such as clarithromycin, roxithromycin, and levofloxacin should be avoided.
Since antibiotics for acne mainly inhibit the reproduction of Propionibacterium acnes, rather than having a nonspecific anti-inflammatory effect, it is important to prevent or slow down the development of resistance in Propionibacterium acnes, which requires the use of antibiotics for acne to regulate the dose and duration of treatment. Usually, the dose of minocycline and doxycycline is 100-200 mg/d, which can be taken orally once or twice; tetracycline 1.0 g/d, taken orally twice on an empty stomach; erythromycin 1.0 g/d, taken orally twice. The duration of treatment is 6-12 weeks. Antibiotic treatment of acne should pay attention to how to avoid or reduce the development of drug resistance. These include:
(1) Avoid using them alone to treat acne, especially for long-term topical application;
(2) Start treatment with a full dose, and do not reduce the dose once it is effective;
(3) Discontinue or switch to other antibiotics when there is no effect after 2-3 weeks of treatment, and pay attention to patient compliance and differentiate between gram-negative bacillary folliculitis;
④Adequate duration of treatment should be ensured and intermittent use should be avoided;
⑤Propionibacterium acnes is a parasitic bacterium of normal skin, and treatment should be aimed at effectively inhibiting its reproduction, not at complete elimination, so the dose should not be unprincipledly increased or the course of treatment prolonged;
(6) If conditions permit, the drug resistance of Propionibacterium acnes can be monitored to guide the rational use of drugs in clinical practice. Adverse reactions should be noted during treatment, including the more common gastrointestinal reactions, drug rash, liver damage, photosensitivity reactions, vestibular involvement (e.g., dizziness, vertigo) and benign intracranial pressure elevation (e.g., headache). Rare adverse reactions include lupus-like syndrome, especially when applying minocycline, and should be used with caution or prohibited in patients with chronic alcohol consumption, hepatitis B and photosensitive dermatitis. Tetracyclines should not be used in pregnant women and children under 16 years of age.
Minocycline can be partially mitigated by dividing the daily dose of minocycline into oral doses, or by using the extended-release dosage form once a night. Discontinue the drug promptly if serious adverse reactions occur or are intolerable to the patient, and treat the symptoms. Macrolides and tetracyclines are prone to drug interactions, so attention should be paid to drug interactions when combined with other systemic drugs.
Treatment of acne with retinoic acid
Oral isotretinoin is the standard treatment for severe acne and is currently the most effective treatment for acne. Isotretinoin acts on all pathophysiological aspects of acne, and although it is effective, it is not the treatment of choice for mild acne due to its adverse effects.
Indications for the use of oral isotretinoin:
(1) Severe nodular cystic acne and its variants;
(ii) Inflammatory acne with scar formation;
(3) Moderate to severe acne that has failed to respond to the following treatments: 3 months of combination therapy, including systemic tetracycline application;
④Acne patients with severe psychological stress (disfigurement phobia);
⑤ Gram-negative bacillary folliculitis;
(6) Patients with frequent recurrence requiring repeated and long course systemic antibiotics;
(7) A small number of patients who need rapid healing for some reason. Dose: The common dose is 0.25-0.5 mg/(kg・d), in order to reduce adverse effects, the dose should not exceed 0.5 mg/(kg・d). The duration of treatment is determined by the patient’s body weight and the daily dose used. The minimum cumulative dose is targeted at 60 mg/kg, but can be increased to 75 mg/kg if a cumulative dose of 60 mg/kg does not achieve satisfactory results.
However, even if Grade 1 acne is completely cleared, the probability of permanent cure is significantly reduced if isotretinoin is discontinued before the 60 mg/kg domain is reached. So-called shock therapy, in which isotretinoin is administered at 0.5 mg/(kg/d) for the first 7 days of the month, has been shown to be effective in patients who have relapsed after a full course of treatment, in those with prolonged disease and in those with treatment-resistant acne.
In some conditions, such as adolescents with severe acne, continuous low doses of isotretinoin can be used to treat these patients with poor initial acne resolution, but isotretinoin 10-20 mg/d for 4-6 months can clear the lesions more quickly, followed by topical retinoids to maintain efficacy. High-dose retinoic acid therapy is not advocated because the improvement in efficacy is not significant, and potentially serious toxic effects may occur.
It is important to counsel and explain to the patient that retinoic acid can cause many adverse effects, especially teratogenic effects, before systemic administration of retinoic acid. Patients should use strict contraception for 1 month prior to treatment and for 3 months after the end of treatment. If pregnancy occurs during the course of treatment, abortion must be performed. A small number of patients may experience depressive symptoms with the use of retinoic acid. Patients with a history of depression or a family history of depression should use caution and discontinue the drug immediately if mood swings or any depressive symptoms occur.
Other adverse effects of isotretinoin are mainly dryness of the skin mucosa. Transient exacerbation of acne may occur in the initial phase. 5% of patients may experience photosensitivity, joint and muscle pain, severe night blindness during night driving, severe hair loss, and possible elevation of blood triacylglycerols. Liver function and lipid tests are performed before the start of treatment and are repeated after 1 month of treatment. If they are normal, no further hematologic testing is required.
Long-term high doses may cause epiphyseal deformities such as osteomalacia, spinal ligament calcification, and osteoporosis. It should be noted that isotretinoin should not be used in conjunction with tetracyclines or systemic glucocorticoids, as isotretinoin and glucocorticoids may synergistically induce an increase in intracranial pressure. However, oral absorption is slightly poorer, the effect is slower, and the adverse effects are relatively mild.
6. Hormonal treatment of acne
6.1 Estrogens Estrogens include estrogen and progestin. It is believed that androgens play a role in the pathogenesis of acne. Female patients with moderate to severe acne should be treated with estrogen and progestin as early as possible if they have high androgen levels, high androgen activity such as seborrhea, acne, hirsutism, androgenic alopecia (SAHA) or polycystic ovary syndrome (PCOS). Combination of contraceptives may also be considered for women with late-onset acne and those whose acne worsens significantly before menstruation. The U.S. Food and Drug Administration (FDA) has approved birth control pills for the treatment of acne in women >15 years of age.
Mechanism of action of oral estrogen and progestin in the treatment of acne:
(1) Estrogen:
(1) Estrogen has an anti-seborrheic effect by reducing excessive androgen secretion due to ovarian and adrenocortical hyperfunction and by stimulating the synthesis of sex hormone binding globulin (SHBG) in the liver, which reduces the concentration of active androgens in the serum.
(2) Estrogen can increase the amount of SHBG synthesis and decrease the amount of free testosterone.
(3) Estrogen has the effect of reducing the size of sebaceous glands and inhibiting lipid synthesis in sebaceous gland cells.
( 2) Progesterone:
(1) It is an inhibitor of 5-alpha reductase, which can reduce plasma testosterone and dehydrotestosterone through negative feedback inhibition.
(2) It can inhibit the ability of sebaceous gland cells and keratinocytes to convert testosterone.
(3) Cyproterone acetate can also block the binding of androgens to their receptors.
(3) Estrogen and progesterone can also act directly on the sebaceous glands of hair follicles to reduce sebum secretion and inhibit acne production.
Oral contraceptives are a combination of estrogen and progestin, and the choice of the type of oral contraceptive is also very important. Some contraceptives contain androgens, and some synthetic progestins cross-react with androgen receptors to reduce SHBG and increase the amount of free testosterone, which can aggravate or cause acne.
Currently, the most commonly chosen medication for acne is cyproterone acetate tablets (Daine 35, Diane 35, each tablet contains 2 mg of cyproterone acetate + 35 μg of ethinyl estradiol), which are taken daily for 21 d starting on the first day of the menstrual cycle, then stopped for 7 d. The medication is repeated for 21 d after the second menstrual period, and is effective for 2-3 months, with a duration of 3-4 months.
For patients with particularly high seborrhea, the effect of conventional treatment with contraceptives is often poor. Adverse effects include small amount of uterine bleeding, breast distension, upper abdominal discomfort and facial skin redness, weight gain, deep vein thrombosis, and chloasma.
6.1.2 Other anti-androgen therapy
Androstadienone, also known as spironolactone, is an aldosterone compound. Mechanism of action:
(1) Competitive inhibition of dihydrotestosterone binding to receptors in skin target organs, thereby affecting its action and inhibiting sebaceous gland growth and sebum secretion.
②Inhibit 5-alpha reductase and reduce the conversion of testosterone to dihydrotestosterone. The recommended dose is 1~2 mg/(kg・d) for 3~6 months. Adverse effects include menstrual disorders (the incidence of which is positively correlated with the dose), nausea, drowsiness, fatigue, dizziness or headache, and hypercalcemia.
It is contraindicated in pregnant women. It is not recommended for male patients, who may experience breast development and breast tenderness after use. Mecamidine (cimetidine) has a weak anti-androgenic effect, competitively blocking dihydrotestosterone binding to its receptors, but does not affect serum androgen levels, thereby inhibiting sebum production. The recommended dose is 200 mg 3 times daily for 4-6 weeks.
6.2 Application of glucocorticoids
Glucocorticoids are used to suppress androgen secretion caused by hyperadrenocorticism, anti-inflammatory and immunosuppressive effects. Oral glucocorticosteroids are mainly used for acne fulminans or acne conglobata, because these types of acne are often associated with excessive immune and inflammatory reactions. However, it should be noted that glucocorticosteroids themselves can induce acne. Oral administration should only be used in patients with severe inflammation and in small, short-term doses.
Recommended dosage:
(1) Acne vulgaris: Prednisone 20-30 mg/d for 4-6 weeks, then taper over 2 weeks and add oral retinoic acid.
If the condition of acne conglobata or acne fulminans worsens during oral treatment with retinoic acid, prednisone 20-30 mg/d for 2-3 weeks, followed by a gradual reduction in dose over 6 weeks; oral retinoic acid should be discontinued or reduced to 0.25 mg/(kg/d), and the dose should be increased or reduced according to the condition.
Prednisone 5 mg/d or dexamethasone 0.375-0.75 mg/d, taken every night, can inhibit the high secretion of adrenal hormones in the early morning and suppress the production of androgens by the adrenal glands and ovaries, and then gradually reduce the dose after improvement. Fisher et al. believe that high doses of glucocorticoids have an anti-inflammatory effect, while low doses have an anti-androgenic effect.
7.Chinese herbal treatment of acne
Chinese herbal treatment should be divided into different types of acne, and the treatment should be added or subtracted according to the symptoms. For acne with red papules, it is recommended to clear the lungs and stomach; for acne with pustules, it is recommended to detoxify and disperse the knots; for acne before menstruation, it is recommended to regulate the flushing method; for acne with aggregates, post-pigmentation or scarring, it is recommended to activate blood circulation and disperse stasis.
Acupuncture: The acupuncture points of Dazhi, Spleen Yu, Foot San Li, He Gu and Sanyinjiao are often selected.
Auricular acupuncture: The patient’s lung points on both sides of the ear were used as the main acupoints, together with Shenmen, sympathetic, endocrine, and subcortical points buried with Wang Bu Liuxing seeds, which were fixed by external adhesive tape.
Diet therapy: Patients should eat less stimulating food such as high sugar, high fat, wine and spicy food, and eat more vegetables (bean sprouts, bok choy, artemisia, winter melon, loofah, bitter melon, water chestnut) and fruits. Drink mung bean soup regularly to clear lung heat and remove dampness and toxicity. Eat more food with long fiber to keep the bowels open, which is good for preventing acne. In addition, avoid using oil, powder, cosmetics, ointments and creams containing hormones, wash your face twice a day with warm water, do not use strong alkaline soap, wipe off facial grease and dirt, do not squeeze facial papules, pimples and pustules with your fingers to prevent scarring, ensure sufficient sleep, and adjust the function of the digestive system, all of which can help to cure acne.
8.Physical treatment of acne
For acne patients who cannot tolerate medication or do not want to accept medication, physiotherapy is the best choice. Currently, the most commonly used physical therapies for acne are photodynamic therapy, laser therapy, and fruit acid therapy.
8.1 Photodynamic therapy (PDT)
PDT uses specific wavelengths of light to activate the porphyrins metabolized by Propionibacterium acnes. Currently, blue light alone (415 nm), blue light combined with red light (630 nm), and red light + 5-aminoketovaleric acid (5-ALA) are used to treat various types of acne vulgaris. The treatment protocol: 48 J/cm2 for blue light and 126 J/cm2 for red light once or twice a week for 4 to 8 treatments.
There was slight itching during the treatment, and some patients showed slight flaking after the treatment, but no significant adverse effects were found. It was demonstrated that photodynamic therapy could inhibit sebaceous gland secretion, reduce the number of acne and inflammatory lesions, and promote tissue repair to varying degrees.
8.2 Fruit acid therapy is widely found in fruits, sugar cane and yogurt in nature. The mechanism of action of fruit acids is to reduce the adhesion of keratinocytes by interfering with the binding force on the cell surface, accelerate the shedding and renewal of epidermal cells, and stimulate the synthesis of dermal collagen to enhance moisturizing function.
The higher the concentration of fruit acid, the longer the duration of action, the better the effect, but also the greater the relative adverse effects. Treatment regimen: Apply 20%, 35%, 50% and 70% concentrations of fruit acids (hydroxyacetic acid) to treat acne once every 2-4 weeks, with 4 treatments. Inflammatory lesions and non-inflammatory lesions showed varying degrees of regression, with a 30% to 61% regression rate. Increasing the number of treatments can improve the efficacy.
8.3 Laser therapy
The 1 450 nm laser, intense pulsed light (IPL), pulsed dye laser and fractional laser are among the most effective treatments for acne and acne scarring, and can also be combined with medications.1 The 450 nm laser is an FDA-approved laser for the treatment of acne. Intense pulsed light can help fade the red marks in the later stages of inflammatory acne. Fractional lasers have shown some improvement in acne scarring.
8.4 Other treatments
This is one of the most effective methods of acne treatment, but medication must be used at the same time to suppress the root cause and development of acne.
Glucocorticoid injection into nodules and/or cysts helps to rapidly eliminate inflammation and is a very effective treatment for larger nodules and cysts.
Cyst excision and drainage: For large cysts, excision and drainage is an effective way to avoid future lesion mechanization and scar formation.
9.Grading of acne
The grading of acne reflects the severity of acne and the nature of the lesions, so the treatment of acne should be based on the grading of the corresponding drugs and methods.
Whether acne is graded according to the International Modified Classification, which is based on the number of lesions, or according to 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 static 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 retinoids are the best choice. Medical skin care products that have the ability to exfoliate, dissolve acne, inhibit sebum secretion, and be antibacterial can also be used as an adjunctive treatment.
Grade 2: Usually treated as Grade 1 acne, but oral antibiotics may be used for those with more inflammatory papules and pustules, and where topical treatment is not effective. Combination therapy, such as oral antibiotics combined with topical retinoids, or physical therapy such as blue light, photodynamic therapy, or fruit acid therapy, may also be used for this type of acne.
Grade 3: Patients in this category often require a combination of treatments, with systemic antibiotics as one of the basic treatments and a sufficient course of treatment. The most commonly used combination therapy is oral antibiotics combined with topical retinoids or topical benzoyl peroxide. Hormonal therapy has also been used with good results in women 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, as well as to the development of photosensitivity. For poor results, oral isotretinoin alone can be used, as well as topical peroxymethylphenidate. For those who need to use antibiotics systematically for more than 3 months, the combination of peroxymethol, an antibacterial agent that does not cause bacterial resistance, is necessary 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 and peroxynivalenol may be used before switching to oral isotretinoin for lesions such as cysts and nodules. Combination therapy as described above for grade 3 acne and as described in this guideline may also be tried. Regardless of the level of acne, it is important to maintain treatment once symptoms have improved.
10. Combination therapy for acne
The combination of oral antibiotics and topical retinoids can have a synergistic effect through their different routes of action, and the combination of these two methods can clear inflammatory damage and acne faster than antibiotics alone. Topical retinoids can also shorten the duration of antibiotic treatment, increase penetration of antibiotics and increase follicular cell turnover, thus allowing more antibiotics to reach the sebaceous units and reducing the incidence of drug resistance.
Combination therapy is now the standard of care for mild to moderate acne, with the following advantages:
(1) The clinical efficacy of antibiotics combined with topical retinoic acid is significantly better than that of antibiotics alone;
(ii) Faster onset of action on inflammatory damage and acne;
(3) It can target different pathophysiological factors;
④ Topical retinoic acid can increase the penetration of antibiotics and promote the rapid action of antibiotics.
Principles of combination therapy:
(1) Oral antibiotics combined with topical retinoic acid can act on all three pathogenic factors;
(2) Oral antibiotics should not be combined with topical antibiotics (which may increase bacterial resistance without increasing efficacy);
(3) The incidence of drug resistance can be reduced by combining peroxybenzoyl or topical retinoic acid with oral antibiotics;
(4) When prolonged use of antibiotics is required, topical benzoyl peroxide should be used in combination;
(5) The combination of topical retinoic acid and benzoyl peroxide can be used daily or alternately with one or both drugs in the morning and evening.
11. Maintenance treatment of acne
11.1 Importance of maintenance therapy
At the end of a course of systemic isotretinoin and antibiotics, if the acute acne symptoms have improved (improvement rate > 90%), maintenance therapy should be considered as much as possible to prevent recurrence, because all current treatments for acne only inhibit the pathogenesis of acne, not cure it. Therefore, maintenance therapy after treatment is necessary. After the initial systemic treatment, topical retinoic acid is the mainstay of maintenance therapy, and in the presence of inflammatory damage, a combination of benzoyl peroxide may be considered.
11.2 The need for maintenance therapy
(1) Microcomedones are an early pathological process in all acne lesions;
②The process of microcomedema formation remains permanent and persistent after acne clearance;
③Avoiding the formation of microcomedones has an acne-preventive effect;
(4) The main mechanism of action of retinoic acid is to interfere with the pathological process of microcomedema.
11.3 Maintenance regimen
(1) Topical topical retinoic acid: Topical topical retinoic acid is the main choice for maintenance treatment;
②Duration of maintenance treatment: 6 to 12 months;
(3) Peroxymethylphenidate: Combination with topical retinoic acid may reduce resistance after antibiotic therapy;
④2nd line of treatment: azelaic acid and salicylic acid.