Acne: acne vulgaris

LAST UPDATED: Jan 16, 2024

Acknowledgements: I would like to thank Professor Bill Cunliffe, Dr. Alison Layton (Consultant Dermatologist at the Harrogate and District Foundation Trust), Dr. Daron Seukeran (Consultant Dermatologist at James Cook University Hospital), Dr Tom Poyner (retired GPwSI in Teesside) and the British Skin Foundation, which funds high-quality research into skin disease and skin cancer.

Patient Information Leaflet
Link: Acne vulgaris

https://www.pcds.org.uk/patient-info-leaflets/acne-vulgaris

Introduction

Virtually every adolescent has a few “spots”, however, about 15% of the adolescent population have sufficient problems to seek treatment. In most patients, but not all, the acne clears up by the late teens or early 20s. More severe acne tends to last longer. A group of patients have persistent acne lasting up to the age of 30 to 40 years, and sometimes beyond. Patients with persistent acne often have a family history of persistent acne. Acne may scar - most of the time this is preventable by using the correct treatment given in a timely fashion.

This chapter is set out as follows:


Aetiology

The aetiology of acne has four major features

  • Androgen-induced seborrhoea (excess grease)
    • The more sebum (grease) the greater degree of acne
    • Sebum is produced by the pilosebaceous glands, which are predominantly found on the face, back and chest
    • Evidence suggests that in most patients the seborrhoea is due to increased response of the sebaceous glands to normal levels of plasma androgens
       
  • Comedone formation (blackheads, whiteheads and microcomedones), which is known as comedogenesis
    • Is due to an abnormal proliferation and differentiation of ductal keratinocytes
    • It is controlled, in part, by androgens
    • In pre-pubertal subjects comedones are seen early and they precede the development of inflammatory lesions
       
  • Colonisation of the pilosebaceous duct with cutibacterium acnes (C. acnes - formerly known as P. acnes)
    • Is a later stage in the development of acne lesions (especially inflammatory lesions)
    • The seborrhoea and comedone formation alter the ductal micro environment, which results in colonisation of the duct
    • C. acnes is the most important organism
       
  • Production of inflammation. This is a complex process involving an interaction between:
    • Biological changes occurring in the duct as a result of comedone formation and C. acnes colonisation of the duct
    • And the patients cellular (especially lymphocytes) response within the dermis, which responds to pro-inflammatory cytokines spreading from the duct to the dermis


Factors which can/might modify acne

  • Hormonal factors
    • About 70% of females will notice an aggravation of the acne just before or in the first few days of the period
    • Polycystic Ovarian Syndrome (PCOS) / other endocrinological disorders
       
  • UV light can benefit acne
     
  • Stress
    • This is a controversial issue - there is some evidence that stress makes acne worse but data to support this view is limited
    • Stress may manifest itself as acne excoriee, where patients, usually females, habitually scratch the spots the moment they appear (refer to the related conditions at the top of this page)
       
  • Diet - although the evidence for a link between diet and acne is not strong, some people with acne have reported improvement in their skin when they follow a low-glycaemic index diet, which can be achieved by:
    • Increasing the consumption of whole grains, fresh fruits and vegetables, fish, olive oil, garlic
    • Decreasing the consumption of high-glycaemic index foods such as sugar, biscuits, cakes, ice creams and bottled drinks
       
  • Cosmetics
    • Caused by oil-based cosmetics
    • Pomade acne is caused by hair pomades, with comedonal and papulopustular acne on the forehead and temples
       
  • The following drugs may cause acne:
    • Topical and oral corticosteroids
    • Anabolic steroids
    • Lithium
    • Ciclosporin
    • Iodides taken orally, which may be part of some homoeopathic therapies

Clinical findings

  • Greasy skin (seborrhoea)
  • Distribution
    • The most common sites are the face and upper trunk
    • Patients with moderate-severe acne may also have lesions on the posterior neck, if these lesions persist then they are likely to be part of the hidradenitis suppurativa (HS) spectrum, such patients may go on to develop other lesions at typical HS sites - see the related chapter for more information
  • Morphology
    • Non-inflamed lesions ie comedones - blackheads and whiteheads (these can be difficult to see, stretching the skin usually helps)
    • Inflamed lesions - papules, pustules and nodules
  • Scarring, which may be due to:
    • Loss of tissue, the so-called atrophic or ice pick scar
    • Increased fibrous tissue, the so-called hypertrophic or keloid scar
  • Pigmentation, which can be a problem especially in skin of colour 

Images

Please refer to notes on image rights at bottom of the page with regards to individual image ownership.


Investigations

  • The vast majority of patients with acne do not require investigations
     
  • Total testosterone and SHBG levels should be checked in patients suspected of having Polycystic Ovarian syndrome (PCOS), which may be suggested by oligomenorrhoea (less than nine periods a year) and/or hirsutism. For further information refer to the chapter Hyperandrogenism 
  • If a patient with mild hyperandrogenism does not have PCOS then consider late onset (non-classical) congenital adrenal hyperplasia. For further information refer to the chapter Hyperandrogenism
  • For patients suspected of having more serious pathology, including those found to have repeat testosterone levels > 4.8 nmol/l (preferably measured in the first 5 days of the menstrual cycle) and/or other features of virilisation, refer to the chapter Hyperandrogenism

Management

Management overview

  • Refer to the top right of the page for a patient information leaflet available through a QR code or printable PDF

  • The following drugs can exacerbate acne: anabolic steroids, topical and oral corticosteroids, unopposed progestogens, lithium, ciclosporin, iodides taken orally (found in some homoeopathic therapies)
  • When choosing treatment it is important to consider the types of lesion:
    • Comedone (figure 1)
    • Papule-pustule (figure 2)
    • Nodule (figure 3)
    • Scarring (figure 4)
  • It is also vital to assess the psychological impact ie what is mild acne to a health professional may be causing severe distress to a patient - a lower threshold for referral should be considered for patients with severe psychological distress

Treatment (read in conjunction with the notes below on 'additional considerations' including acne management in pregnancy)

Step 1: Mainly comedonal acne - a topical retinoid
  • Choices include adapalene (Differin ®), adapalene combined with benzoyl peroxide (Epiduo 0.1% ®), and trifarotene (Aklief ®)
  • In order to reduce excessive dryness/irritation advise patients to leave on for 30-60 minutes before washing off, then gradually increase the duration of treatment as tolerated (eventually many patients can apply at bedtime and leave on overnight)
Step 2: Mild to moderate papular / pustular acne

Use a fixed dose combination treatment, ideally containing benzoyl peroxide (BPO), which reduces bacterial resistance, with either a topical retinoid or topical antibiotic:

  • ​First-line: Epiduo ® 0.1% or 0.3% gel (adapalene + BPO)
  • Second-line: Duac ® gel (clindamycin + BPO) or Treclin ® gel (clindamycin and tretinoin)
  • Other options: Aknemycin ® Plus solution (erythromycin and tretinoin)
  • Any topical retinoid or benzoyl peroxide can be used on its own if combination products are not tolerated
  • Advise as step 1 regarding adverse effects
Step 3: Not responding to the above and/or more widely distributed (without significant scarring)

Combine systemic antibiotics with an appropriate topical agent, preferably Epiduo ® 0.1% or 0.3% gel or if not tolerated use BPO, adapalene, or trifarotene (Aklief ®) as single agents. Choice of antibiotic:

  • First-line: lymecycline 408 mg OD or doxycycline 100 mg OD, if partial response consider increasing the dose of either to BD (both contraindicated in pregnancy and children under 12 years of age)
  • Second-line: check with local guidelines as there are several options -
    • The tetracycline not used above as first-line
    • Clarithromycin 250-500 mg BD - higher levels of bacterial resistance than tetracyclines, but lower when compared to erythromycin
    • Trimethoprim 300 mg BD - patients need to be counselled as to the very small risk of severe cutaneous adverse reactions, and agranulocytosis (patients and their carers should be told to seek immediate medical attention if symptoms such as fever, sore throat, rash, mouth ulcers, purpura, bruising or bleeding develop. The BNF also recommends regular FBC)
  • Additional options in women - hormonal treatments and/or spironolactone 
    • See below for notes on hormonal treatments
    • Spironolactone - can be used with a topical treatment instead of or in addition to antibiotics or hormonal treatments:
      • Renal function should be checked prior to starting. Monitoring is only required in the over 45's or in certain at risk populations
      • Commence at a dose of 50 mg once a day, increasing to maximum of 200 mg daily according to response and adverse effects 
      • Is contraindicated in pregnancy due to the risk of feminisation of a male foetus
  • Children under 12 years of age: clarithromycin (dose dependent on weight)
  • Duration of systemic antibiotic treatment
    • Ideally 3 months, evidence suggests that for most patients there is little additional benefit in using antibiotics for more than 3 months in any given treatment period - however, patients relapsing quickly after stopping treatment may be better suited to 6 month courses
    • Once stopped, many patients will need to remain on their topical agent (step 2)
    • The antibiotic course can be repeated in the future if needed
Step 4: Active scarring acne
  • Patients with active acne and significant scarring should be started on treatment (as in step 3) and referred at the same time as semi-urgent (ideally to be seen within 6-12 weeks). The only exception may be some cases of early scarring in mild-moderate papulopustular acne (as opposed to nodular), when it may be deemed appropriate to commence treatment (as in step 3) and review at 6 weeks - if there are no signs of significant improvement then refer

Treatment - additional considerations

Hormonal treatments 

  • Can be used on their own, or in combination with the topical / systemic treatments referred to above, and may be of particular value in patients with significant endocrinopathies such as PCOS
  • While Dianette has been used historically to treat acne, it is likely that some cases of acne will benefit from alternative combined oral contraceptive pills (COCPs) with a lower oestrogen content (20 mcg) and a better safety profile. Accordingly, a trial of either Eloine or Mercilon could be considered as first-line and failing that Dianette could be considered if not contraindicated. The Faculty of Sexual and Reproductive Healthcare also promote tricycling of COCPs taking 9 consecutive weeks before having a 4-7 day break. It is also worth noting that the risk of venous thromboembolism is greater if Dianette/other COCPs are stopped and started as opposed to being kept on (if required)

Acne in pregnancy

  • The mainstay of treatment should be topical treatment, either benzoyl peroxide preparations or 2% topical erythromycin. In terms of topical retinoids, systemic exposure is thought to be negligible; however, since risk cannot be excluded, the use of topical retinoids is contraindicated during pregnancy as a precaution, additionally, female patients should be advised to avoid topical retinoids if they are planning a pregnancy
  • The option of oral erythromycin 500 mg BD should be discussed with the patient if the potential benefits outweigh the possible risks, for example in scarring acne

    Acne in skin of colour 

    • Acne is no more common or severe in skin of colour skin, but post-inflammatory hyperpigmentation can be significant and often persists for months to years. As such, early and more aggressive treatment is advocated, including early referral for consideration of isotretinoin
    • Secondary acne can be a result of cultural practices - hair oil can induce pomade acne on the forehead and skin lightening products containing topical steroids can cause a steroid-induced acne 
    • Topical retinoids, benzoyl peroxide and azelaic acid play an important role in the treatment of the comedonal aspects of acne. If used daily they often cause dryness and irritation, which in skin of colour skin can lead to further hyperpigmentation. Accordingly these treatments should initially be used for shorter periods of time (eg in an evening and washed off before bed) and perhaps less frequently (eg every 2nd or 3rd day), if tolerated the duration and/or frequency of treatment can be increased - if used in this way then as well as treating the comedones they may help treat hyperpigmentation rather than aggravate it  

    Post-inflammatory hyperpigmentation 

    • Post-inflammatory changes tend to improve very slowly
    • One treatment that may help some patients is Eucerin DermoPurifyer Post Acne Marks ® (non-NHS)

    Referral - Secondary Care or Community Dermatology services described below

    Who to refer

    • Severe acne - refer early
    • Moderate acne only partially responding to treatment and starting to scar and/or causing significant hyperpigmentation (more common in patients with skin of colour)
    • Patients with associated and severe psychological symptoms, regardless of the physical signs

    If referring for possible isotretinoin please make sure of the following:

    • U&Es, LFTs, and fasting lipids checked
    • Female patients during their reproductive years need to be on appropriate contraception 
    • Provide a patient information leaflet on isotretinoin (alphabetical order) 

    Prescribing isotretinoin in the community

    • Please read the PCDS document (Oct 31st 2023) related to the regulatory changes regarding isotretinoin including use in the community 

    Scarring

    Up to 50% of scars (especially smaller scars) may improve naturally over 6-12 months. Treatment of established scars is difficult and while some patients will benefit from treatment others will not. Patients should only be referred to dermatologists / plastic surgeons familiar with treating scars. Funding will vary depending on local commissioning arrangements.

    • Atrophic scars
      • The development of ablative lasers combined with appropriate surgical techniques has led to a significant improvement in the way that certain atrophic scars can be treated
      • Punch excision of small atrophic scars which can be very helpful prior to resurfacing
      • For deep scars - scar revision may help
      • Other options include intradermal injections of collagen or compounds, which stimulate collagen synthesis 
         
    • Hypertrophic / keloid scars
      • Silicone gels applied to scars can be prescribed by general practitioners
      • Local steroids for a trial period of two to three months. Look closely for side-effects such as skin thinning and telangiectasia. Treatments can be administered as topically ie a potent or super-potent steroid cream or ointment carefully applied, Haelan ® tape (fludroxycortide) or by using intradermal triamcinolone given as an injection
      • Pulsed dye laser, which can reduce the redness of scars and flatten them. This procedure is only possible through specialised hospital departments

    Other resources


    Additional images


    Disclaimer - the author PCDS cannot accept responsibility for any misleading or incorrect statements, and the management of individual patients remains the direct responsibility of the individual doctor. We do however hope that visitors to this site can contact us regarding comments that are considered misleading or incorrect so that we can continue to improve the site.

    Image Rights - The PCDS would like to thank Dermatoweb, DermQuest (Galderma), and others who have contributed images. All named individuals and organisations maintain copyright for the relevant images. This website is non-profit and holds the images for educational purposes only. Any image downloaded must only be used for teaching purposes and not for publication or commercial use. Notice and credit must be given to the PCDS or other named contributors.

    Quick Links