Management of acne vulgaris in primary care - what are the best evidences?

Wing-yiu Lai 黎永耀

HK Pract 2007;29:233-241

Summary

Acne vulgaris is a common skin disorder encountered in primary care. Most clinicians are familiar with the diagnostic approaches and the treatment strategies in different grades of acne. However, from the evidence based medicine point of view, are we giving the best care to our patients according to the best available evidences? In this paper, a preliminary evidence based review was performed on the following aspects about management of acne, namely common misunderstandings, topical treatment, oral treatment, adjunctive treatment modalities such as intralesional corticosteroids or chemical peels and remedy for post-acne pigmentation and scarring.

摘要

尋常痤瘡（俗稱普通暗瘡）是一種在基層醫療常見的皮膚疾病。多數醫生對不同類型痤瘡的診斷和治療都很熟悉。 \ 然而，從實證醫學角度，我們是否依據最好的實證為病人提供最佳的治療？本文會以實證對痤瘡治療上的各方面進行初步審訂， 其中包括常見的誤解、局部性治療、口服治療。輔助醫療方式，例如在患處注射類固醇或化學脫皮，與及對痤瘡後的色素和疤痕作出補救。

Introduction

Acne vulgaris is a disease of the pilosebaceous follicles of skin, which are located on the face, back and chest. Four major factors contributing to its pathogenesis include dyskeratinization of the follicular opening, hypertrophic sebaceous glands, androgen stimulation and colonization of Propionibacterium acnes (P.acnes). In other words, it is a complex interplay among genetics, hormones, excess sebum production, blockage of pore openings, bacteria and the body's immune response.

The disease has a wide range of clinical expression and can be classified according to the predominant lesion type.

Non-inflammatory or comedonal acne is primarily composed of open comedones (blackheads) and closed comedones (whiteheads) with little or no inflammatory involvement.

Inflammatory acne is characterized by inflamed lesions (pustules, papules and nodules) and can be further subdivided into papulopustular, nodular and conglobate type depending on the predominant lesion morphology.

Conglobate acne is characterized by clusters of lesions joined by sinus tracts. The older term nodulo-cystic acne is less used now as it is accepted that the cysts are actually abscesses or granulomas.¹

Incidence and prevalence

Acne is extremely common, affecting about 4 in 5 (80%) of adolescents and young adults aged 11 to 30 years. In Hong Kong, it is the 4th most common skin disease seen in social hygiene clinic in the year 2000 and 2001. In primary care setting, according to a recent morbidity survey in four government general practice clinics, it ranks 6th among other skin disorders such as atopic dermatitis or dermatophytosis.²

Diagnosis of acne

Presence of comedones, papules, pustules, cysts and scars over the face, back and chest is highly suggestive of diagnosis. Demonstration of comedones will further support the diagnosis. Before diagnosing acne based on the physical features, the following information needs to be checked:

1. Duration and age of onset.
2. Possible aggravating factors such as hot and humid weather, sweating, emotion and use of cosmetics.
3. Previous treatment for acne: prolonged use of antibiotics may cause gram negative folliculitis.
4. General past health of the patient, particularly on any evidence of systemic disease such as Cushing syndrome. For female patient, any irregular period or hirsutism may indicate the presence of endocrine disorder due to androgen excess, for example, polycystic ovarian syndrome, androgen secreting ovarian or adrenal tumour.
5. Drug history: acne may be aggravated by the use of corticosteroids (topically or systemic); lithium (commonly used in manic depressive patients); and testosterone (used by athletes or body builders).
6. Occupational history: certain chemicals may worsen acne, for example, insoluble cutting oil (in engineering and manufacturing industries), crude petroleum (in oil refining industry), diesel oil (in motor engines) and halogenated aromatic hydrocarbons (in manufacturing conductors and insulators, insecticides, fungicides and herbicides).
7. Family history.

Differential diagnosis

1. Rosacea - it is characterized by flushing with sun exposure, alcohol and spicy food. Inflamed papules and pustules, together with the presence of persistent redness or visible telangiectasia and absence of comedones are some of its diagnostic features.
2. Steroid induced acne - it is induced by the prolonged use of topical steroid cream, or systemic steroid ingestion or injection. The lesions are monomorphic in nature, which means they are uniform in size and appearance.
3. Perioral dermatitis - it is characterized by acne-like papules and pustules locating symmetrically around the perioral area. There is usually a history of inappropriate, prolonged use of topical steroid cream.
4. Gram negative bacterial folliculitis - as the name suggests, it is due to the infection of hair follicles by gram negative organism. It often presents as multiple small inflamed pustules that do not respond to antibiotics against acne. It is caused by the repeated use of anti-acne antibiotics treatment.
5. Pityrosporum folliculitis - it is due to the infection of hair follicles by yeast called Malassezia furfur. It usually presents as small, erythematous papules and pustules around hair follicles on the shoulders, back and chest wall. They tend to be monomorphic in appearance and develop suddenly within a short period of time.
6. Pseudofolliculitis - it mainly occurs in men with curly hairs around the beard region on the chin. It is particularly common in dark skin people.

Searching strategies

The following reference databases were searched, namely the Cochrane Library, Medline, Ovid (including Embase, Clinical evidence and CINAHL). Keywords and MeSH terms were both searched for the following wordings: acne, acne vulgaris, acne keloid, diet, food, cosmetics, squeezing, soap, cleansing agent, retinoids, benzoyl peroxide, azelaic acid, tetracycline, doxycycline, minocycline, erythromycin, topical antibiotics, oral contraceptive, cyproterone acetate, ethinylestradiol, intralesional corticosteroid/steroid, intralesional triamcinolone, chemical peels, glycolic acid, Jessner's solution, trichloroacetic acid, tazarotene, post-acne pigmentation/hyperpigmentation, depressed acne scar, hypertrophic acne scar, scar revision surgery, dermabrasion, fillers injection, laser resurfacing and cryotherapy. With the help of filter engine, only meta-analysis, systematic reviews and randomized controlled trial were included in this article.

Common misunderstandings on acne - any evidence?

1. "Certain food can aggravate acne"

In Chinese culture, there is always a perception that certain food may aggravate acne, for example, the greasy fried food, chocolate and nuts have been quoted to cause flare-up of acne. This may be true according to some traditional Chinese medicine theories but there is no scientific evidence to prove that diet plays a role in causing acne. Interestingly, a recent population based retrospective cohort showed there may be an association between consumption of whole milk and skim milk with increased risk of acne in teenage patients.³ However, the study design cannot prove the decreased intake of milk will improve the acne.

2. "Treatment by beauticians is beneficial to acne"

Facial treatment by beauticians in salons is very common in our locality. However, there is no evidence that these treatments are useful in treating acne. Simple procedures such as cleaning or extraction of open comedones are generally considered safe but further squeezing may result in more complications.

3. "All cosmetic products should be stopped"

Looking good and attractive is important for many people in the modern society. However, no quality evidence is found about the relationship between acne and cosmetic products. If cosmetic use is deemed necessary, it is wise to avoid oily based make-up as they tend to worsen acne. It is also suggested to use preparations that have been labelled "non-comedogenic", "non-acnegenic", "non-irritating", "hypoallergenic" or "specially formulated for oily skin or acne".

4. "Squeezing pimples can help cure the acne"

No quality evidence is found in supporting the role of squeezing pimples. According to some expert opinions, this unhealthy habit can result in greater damage and inflammation to the skin which may lead to more severe scarring and prominent post acne hyperpigmentation.

5. "Dark coloured food can cause pigmentation after acne"

Due to the presence of more pigment in Asian skin, there is higher tendency of pigmentation after acne flare up. Hence, there is no relationship between the use of dark coloured food and post-acne hyperpigmentation.

Evidence based topical treatment for acne

1. Skin cleansing and care

The aim is to remove excessive oil, dirt and bacteria which may be the causative agents of acne. Basically there are two types of cleansing agents; namely ordinary soaps and soap-free syndets (synthetic detergents).

According to the largest double blinded randomized controlled trial (RCT), an acidic soap-free syndet was less irritant than ordinary soap and reduced both inflamed lesions and non-inflamed lesions in 120 patients with mild acne who were not taking any other anti-acne medications.⁴ (No number needed to treat (NNT) can be calculated because of insufficient data in the original text but number needed to harm (NNH) for ordinary soap = 3). Moreover, ordinary soaps are of alkaline pH which can cause itching, dryness and redness. On the contrary, soap-free syndets are usually acidic (pH 5-6 which is similar to normal skin) and hence may be more beneficial to aid treatment of acne. It is wise to clean the face with cleansing agents 2 or 3 times only in a day as excessive washing may result in irritation of skin.

Regarding the addition of topical antibiotics (e.g. Triclosan) or abrasives (such as salicylic acid) in the cleansing products, there is no good quality evidence to support its roles.

2. Topical retinoids

The aim is to reduce the keratinocytes around the openings of the pilosebaceous units which can subsequently reduce the number of closed or open comedones. Tretinoin, isotretinoin and adapalene are the most commonly topical retinoids in the treatment of acne. Tretinoin is commercially available in cream or gel in different concentrations, namely 0.025%, 0.05% and 0.1%. Gel is the most drying preparation and it is advisable to apply it once daily at the lowest concentration initially at night time as sunlight may cause sensitivity to the skin. The skin will usually become red and peeled at the start of treatment but this may improve after a few weeks.

According to a meta-analysis, adapalene demonstrated equivalent efficacy to tretinoin in terms of reducing total lesion count but demonstrated more rapid efficacy, as evidenced by a significant difference in the reduction of inflammatory and total lesions at week 1. (NNT for both adapalene and tretinoin was 2). Adapalene also demonstrated considerably greater local tolerability at all evaluation periods, (NNH comparing tretinoin against adapalene for immediate burning = 4, for scaling = 7, for dryness =10 and for erythema = 14). The findings from this meta-analysis suggested that adapalene 0.1% gel constituted a pharmacologic advance over such classic retinoids as tretinoin for the treatment of acne vulgaris.⁵

3. Topical antibiotics

It aims to decrease the population of P. acnes and is used to treat the inflamed lesions. However, it is not helpful in treating non-inflamed lesions such as open comedones (blackheads) or closed comedones (whiteheads).

Two antibiotics are commonly used in treating inflammatory acnes topically, namely clindamycin and erythromycin. Topical clindamycin is available in 1% concentration as alcohol-based solution, alcohol-free lotion and gel. On the other hand, topical erythromycin is available in 1% to 4% concentrations as alcohol based solution, emulsion or gel. Both antibiotics are equivalent in efficacy according to several small randomized controlled trials conducted years ago,^6-8 (No NNT or NNH can be derived because there is no placebo data for comparison of the efficacy).

Topical antibiotics should be used twice daily on the inflamed acnes and it is generally well tolerated except some mild skin irritation, dryness or redness. Prolonged use as maintenance therapy is strongly discouraged due to the possibility of developing resistant bacterial strains. Moreover, topical antibacterial agents should generally not be used for extended periods beyond 3 months, and topical antibacterial should ideally not be combined with systemic antibacterial therapy for acne; in particular, the use of topical and systemic antibacterial is to be avoided as far as possible due to the concern about the development of resistant bacterial strains.⁹

4. Azelaic acid

The exact mechanism is not well known but it is believed to have keratolytic, anti-inflammatory and antibacterial action. According to 2 systematic reviews, the RCTs identified in the reviews showed significantly reduced number of comedones and inflammatory lesions10,11 but its use is limited by the frequent occurrence of skin irritation.

5. Benzoyl peroxide

It has anti-inflammatory, anti-bacterial and comedolytic properties. It is available in concentrations from 2.5% to 10% as gel, cream or lotion preparations. It is best for mild to moderate inflammatory acnes. Irritation to skin is very common and hence the lowest concentration should be tried initially. If it is tolerated, it can be applied twice daily. According to the same systematic reviews, changes in both non-inflammatory/inflammatory lesions were consistently superior in the Benzoyl peroxide group but no evidence was found to support its dose response effect.^10,11

Combination products containing benzoyl peroxide and the topical antibiotics have been shown both to: (i) prevent the development of antibiotic resistance in acne patients; and (ii) confer significant clinical improvement to patients who have already developed antibiotic resistance.¹²

6. Combination topical therapy

In recent years, there are many new combination products available in the market. Combination products in Hong Kong include Erythromycin + benzoyl peroxide (E&B), Erythromycin + tretinoin (E&T) and Clindamycin + benzoyl peroxide (C&B).

Several well conducted randomized controlled trials have shown efficacy in the use of preparations containing erythromycin + benzoyl peroxide and erythromycin + tretinoin. First, topical benzoyl peroxide/erythromycin combinations are similar in efficacy to oral oxytetracycline and minocycline and are not affected by propionibacterial antibiotic resistance,¹³ (NNT/NNH cannot be derived due to the lack of placebo data for comparison). In another study, Benzoyl peroxide was found to be the most cost-effective topical agent but it was associated with a greater frequency and severity of local irritant reactions. The use of a combination of topical benzoyl peroxide and erythromycin gives less irritation and better quality of life. There was little difference between erythromycin plus benzoyl peroxide administered separately and the combined proprietary formulation in terms of efficacy or local irritation, except that the former was nearly three times more cost-effective.¹⁴ Comparing between E&B and E&T preparation, 3% erythromycin/5% benzoyl peroxide may provide a greater beneficial effect than 0.025% tretinoin/erythromycin 4%, (NNT for E&B against E&T: physician rated severity = 4; patient rated severity = 3). Side effects were controversial because the 3% erythromycin/5% benzoyl peroxide demonstrated significantly greater reduction of erythema (NNH for E&B against E&T for erythema = 8) and scaling as evaluated by the study physician, while patients judged 3% erythromycin/5% benzoyl peroxide to have a significantly greater effect on redness, dryness, oiliness, and burning.¹⁵

Regarding the role of Clindamycin + benzoyl peroxide, it demonstrated improved efficacy and similar tolerability to benzoyl peroxide used alone and was similar to benzoyl peroxide/ erythromycin.¹⁶ A multi-centre, double-blinded controlled study showed that topical clindamycin/benzoyl peroxide combination gel was well tolerated and superior to either individual ingredient,¹⁷ (NNT for clindamycin/benzoyl peroxide = 2, for benzoyl peroxide or clindamycin only = 4).

Evidence based oral treatment for acne

1. Oral antibiotics

Antibiotics are the most commonly prescribed therapy for acne. They are usually the first line oral treatment. It aims to reduce the population of P.acnes as well as to inhibit the action of certain pro-inflammatory chemicals which results in reduction of the severity of acne.

The choice of antibiotics depends on the drug's efficacy, patient acceptability and potential drug interaction with other medications taken by the patients concurrently. Commonly used preparations include tetracycline, doxycycline, minocycline and erythromycin. Among the different antibiotics, minocycline has been evaluated in a systematic review. According to the systematic review, minocycline is likely to be an effective treatment for moderate acne vulgaris. The usual dosage is 50mg twice daily and it can be taken with meals. However, it may cause bluish pigmentation of the skin if used for long term. Moreover, the review found no reliable RCT evidence to justify its continued use as first-line, especially given the price differential and the concerns that still remained about its safety. Its efficacy relative to other acne therapies could not be reliably determined due to the poor methodological quality of the trials and lack of consistent choice of outcome measures.¹⁸

Therefore, tetracycline is still the first choice because it is relatively cheaper than other alternatives in the same group. It is usually prescribed as 500mg twice daily and the clinical response is generally noted around 6-8 weeks. It must be taken on empty stomach or at least 1 hour before meal as its absorption is affected by food. As it is well known to cause permanent discoloration of teeth in children, it must be avoided in kids and pregnant lady.

Doxycycline is another newer generation of the tetracycline group. The usual dosage is 100mg daily and it can be taken with meals. It is generally better tolerated but may cause photosensitivity to some patients.

Regarding the efficacy of erythromycin, it may not be the best choice because no quality RCT was found and there is increasing concern about resistant bacterial strains but it may still be an option for patients who are intolerable to tetracycline or for women planning pregnancy or who are pregnant. The usual dosage is 500mg twice daily. Its common side effects are usually mild and may include diarrhoea, vomiting and flatulence. If erythromycin gives poor response, azithromycin or roxithromycin may be considered because several small scale RCTs showed azithromycin and roxithromycin were as effective as the tetracycline group in the management of acne.^19,20 (No NNT can be calculated based on the data available in the original text). However, their roles in management of acne remain to be confirmed.

2. Hormonal therapy

It is not only a contraceptive, but also a very effective systemic treatment in women with inflammatory acne. It aims to decrease the androgen stimulation of the sebaceous gland (resulting in decreased seborrhea) and the keratinocyte (resulting in decreased follicular dyskeratinization) which end up with decreased colonization and inflammation of the acnes. The preparation used in Hong Kong combines an anti-androgen, cyproterone acetate 2mg and an estrogen, ethinylestradiol 0.035mg (C&E). The woman taking this drug must not be pregnant or breast feeding and should not have history of liver disease or deep vein thrombosis. The common side effects include headache, nausea, vomiting, breast tenderness and weight changes but these are usually transient and will be resolved after a few months. Regarding the evidence on its efficacy, a recent systematic review showed that preparation containing C&E was effective in reducing inflammatory and non-inflammatory acne lesions.²¹

3. Oral isotretinoin

Isotretinoin belongs to a class of drug called retinoids. It is the most powerful tool in treating nodulo-cystic acne and severe acne that does not respond to other treatment modalities. It aims to decrease the sebaceous gland activity, prevent comedone formation, reduce the P. acnes population indirectly as well as the associated inflammation. It is available in 10 or 20 mg capsules. The dosage is based on the body weight of patients and it varies from 0.5 to 1.0 mg/kg/day. The usual duration of treatment is 4 to 6 months. After the initial 1-2 weeks of treatment, the patients will usually feel the skin become less oily and 3-4 weeks later, they may show signs of acne clearing. Its use is supported by a meta-analysis which consistently proved isotretinoin to be a highly effective agent in the treatment of moderate to severe acne vulgaris. The response rate determined by the meta-analysis indicated a clinical cure in 84.22% to 86.71% of patients treated. From the data considered, the average treatment duration was calculated to be 17.9 weeks (4 months). The relapse rate was low (21.45%) and dose-dependent. Optimal results were achieved by treating patients with a daily dose of 1 mg/kg to a target cumulative dose of 120 mg/kg over the treatment duration.²²

Before its initiation, the side effects must be explained well to the patients. The most important one is teratogenicity. Pregnancy must be avoided during the following period: 1 month before the initiation of the medication, throughout the time when the patient is taking the medicine and 1 month after it has been stopped. Moreover, a reliable method of contraception must be used for all sexually active women. Besides the contraception issues, patient should be reminded to avoid donating blood or exposing to too much sunlight. In addition, the common side effects are mainly muco-cutaneous which include dry and sore lips (may be relieved by vaseline or lip moisturizer); dry eyes (may be relieved by artificial eye drop); dry skin (may be relieved by liberal use of moisturizer); dry mouth (may be relieved by fluid drinking) and nasal crusting (which may cause nose bleeding). Less common side effects include alopecia, myalgia, headache and nausea and these are more frequent when higher doses are used. Other side effects that must also be mentioned are blood dyscrasia, liver impairment and lipid profile derangement. Hence, pre-treatment checking of complete blood picture, liver function test and regular monitoring of lipid profile is recommended. Concerning the relationship between isotretinoin therapy and the risk of depression, psychotic symptoms, suicide or attempted suicide, a large population based retrospective cohort has failed to confirm the association.²³

Other treatment modalities - an evidence based review

1. Intralesional corticosteroids

It aims to quickly decrease the inflammation of large acne cysts which usually take weeks to resolve on their own. The injection, e.g. triamcinolone is performed with a small gauge needle and the procedure is generally safe and not painful. The cyst will usually resolve within days but repeated treatment may be needed if the cyst recurs again. It is preferable to incision and drainage as the latter procedure may easily result in permanent scarring and its use is supported by a small RCT conducted 2 decades ago,²⁴ (No NNT or NNH can be derived due to the absence of initial score for comparison in the original text).

2. Chemical peels

It aims to unblock the follicular openings and hence can improve the mild acne lesions which are predominantly comedones. Several sessions are required and complications are generally uncommon though pigmentation or scarring may occur in Asian skin after the chemical peels treatment. The most commonly used agents are glycolic acid (e.g. alpha-hydroxy acids (AHAs)), Jessner's solution and trichloroacetic acid with regard to its efficacy, a small RCT showed benefits of glycolic acid and Jessner's solution in the treatment of facial acne. Glycolic acid is less widely used due to its inconvenient application technique but considering the equal treatment effect and lesser degree of exfoliation in glycolic acid, it is still recommended to use glycolic acid instead of Jessner's solution for acne patients,²⁵ (NNT or NNH cannot be calculated because no placebo was available for comparison).

3. Treatment of post-acne pigmentation

It is very common to have post acne pigmentation in Asian patients especially when there is history of severe inflammation, picking, squeezing or minocycline use. The pigmentation will generally become lighter with time but the remaining appearance is still causing cosmetic concern. No good evidence is found regarding the role of lightening creams (e.g. hydroquinones), chemical peels, intense pulse light therapy or lasers in minimizing the pigmentation and they may even cause further damage to the skin. The only agent which may be helpful is tazarotene 0.1% cream. According to a small double-blind, randomized, vehicle-controlled trial, once-daily application of tazarotene cream was shown to be effective and well tolerated in the treatment of PIH in patients with darker skin,²⁶ (NNT for overall disease severity = 5; pigmentary intensity of hyperpigmented lesions = 6; area of hyperpigmented lesions = 8). However, this study is targeted at the dark skin individuals and this product is not yet available in Hong Kong.

4. Treatment of acne scarring

(a) Depressed acne scars

There are several types of depressed acne scars according to the classification by the dermatologists, eg. ice-pick scars, box-car scars and rolling scars. There is no effective method to totally eliminate this type of scar but currently, the following procedures are popularly used:

(i) Scar revision surgery:

It is claimed to improve the appearance of deep scars, e.g. deep box-car scars or ice-pick scars. The procedure involves the excision of the scarring skin and closure of the wound by stitches. This is usually performed under local anaesthesia and may need several sessions to achieve the best cosmetic outcome. Further improvement of the residual scars may become possible by other non-surgical means. However, there are still no well conducted studies confirming its role in treatment of deep acne scars.

(ii) Dermabrasion:

It is the most invasive procedure which involves manual removal of the superficial skin layer (down to the upper dermis) by a small hand-held dermabrader. It is very traumatic and gives variable results depending on the surgeon's technique. Hence it becomes a less favourite and is replaced by ablative laser device nowadays. Moreover, no quality evidence is found concerning its usefulness.

(iii) Fillers injection:

Recent advances in technology allow the injection of filler substances into the dermal layer which results in elevation of the depressed scars. The effect will usually last for about 4 to 6 months because the material injected will eventually be adsorbed by the body. However, there is again no quality evidence found regarding its efficacy.

(iv) Chemical peels:

It is claimed that superficial depressed scars may also respond to repeated chemical peeling procedures. However, special caution must be paid on the possibility of pigmentation after treatment. Moreover, there is no quality evidence to support its use in facial acne scar.

(v) Laser resurfacing:

Ablative laser resurfacing is aimed to destroy the surface of the skin down to the upper dermal layer and thus allows the underlying dermal collagen tissue to heal and remodel itself which will result in improving the appearance of the depressed acne scar. It is considered to be one of the most effective methods to treat these kinds of scarring (around 30-40% improvement according to expert's opinion). However, this method involves a significant "downtime" for the patient and careful wound care is essential to prevent secondary bacterial or viral infection. Moreover, post-treatment erythema and pigmentation are common and may even become permanent.

The advance of cooling devices in new laser machines e.g. non-ablative laser resurfacing allows the selective heating of the dermal collagen layer without damaging the epidermis. There is no "downtime" for the patient receiving this treatment and the procedure can generally be performed with minimal or no anaesthesia. The cosmetic effect is the best for shallow scars and it is quoted to bring about 15-20% improvement from expert's opinion. However, according to a systematic review, there is lack of good quality evidence to support the role of laser in the management of acne scarring.²⁷

(b) Hypertrophic acne scars

Silicon gel sheets and scar creams over the counter are not effective to treat these kinds of scarring. Partial improvement may be achieved by injection of corticosteroids or cryotherapy according to a small RCT.²⁸ (No NNT can be derived from the data available in the original article).

Psychological aspect of acne

Acne is particularly important in adolescents. Its impact to patient might not be proportionate to the size, number, redness or pain of the skin lesions. The resultant quality of life impairment and psychic sequelae such as depression, eating disorder and body dysmorphic disorder are equally important. A thorough understanding of the patients by using validated questionnaires, e.g. Cardiff Acne Disability Index, observing the associated behaviour changes, performing individualized counselling and offering discussion of the nature and method of therapy may optimize their well-beings.²⁹

Conclusion

According to the level of evidence, the following conclusion regarding different treatment modalities for acne can be drawn:

Evidence supported by meta-analysis/ systematic review

- topical retinoids (preferably adapalene)
- topical benzoyl peroxide
- topical azelaic acid
- oral antibiotics (tetracycline group)
- hormonal therapy (for female only)
- oral isotretinoin

Evidence supported by RCTs

- soap free syndets
- topical antibiotics
- topical combination therapy
- intralesional triamcinolone for large acne cysts
- chemical peels for mild acne lesions
- topical tezarotene cream for post-acne pigmentation
- injection of corticosteroids or cryotherapy for hypertrophic acne scar

Inconclusive evidence

- common misunderstandings concerning the management of acne
- topical antibiotics or abrasives in cleansing products
- oral antibiotics (erythromycin)
- treatment methods for depressed acne scar such as scar revision surgery, laser resurfacing, chemical peels, fillers injection or dermabrasion

Acknowledgement

I would like to give my sincere thanks to Dr Luke Tsang, Consultant in Family Medicine, Professional Development and Quality Assurance, Department of Health for his kind support in preparing this manuscript for publication.

Key messages

1. Most of the current topical and oral treatment for acne is evidence based and they are supported by meta-analysis/systematic review/ RCTs.
2. The role of adjunctive treatment in management of hypertrophic scar and post-acne hyperpigmentation is also evaluated by RCTs.
3. The evidence for topical antibiotics/abrasives in cleansing products and treatment of depressed acne scar is still inconclusive.