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Truncal Acne: Acne on the Chest and Back

Truncal Acne, acne vulgaris on the chest, shoulders, and back, is an extremely common, but often undertreated entity.

Published on 10/22/2020
AcneDermatologistSkin CareSkin
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Truncal Acne, acne vulgaris on the chest, shoulders, and back, is an extremely common, but often undertreated entity. It has been reported that only 25% of patients with truncal acne voluntarily provide this information to their dermatologist, but most (78%) do want treatment.1 Truncal acne often goes untreated because patients are embarrassed to show their doctor, dermatologists do not inquire about it, and truncal acne often covers a large area difficult to treat with topical medications.2 However, it is extremely important for dermatologists to recognize and treat this entity, due to the potential for scarring. Prevention of scarring through early detection and treatment of truncal acne is important and necessary, given that treatment of truncal scars can be challenging.


When encountering a patient with acne, it is important to ask the patient about involvement of chest, shoulders, and back. This information is often not voluntarily provided by the patient but critical in deciding treatment options. The physician should also examine the trunk to determine if there is indeed involvement of these areas and to what degree. Acne severity is dependent on lesion size, density, type, and distribution of the lesions. The CASS grading scale is a simple and effective way to grade the severity of facial and truncal acne. 3

CASS Grading Scale3



Almost clear




Very severe

Differential Diagnosis

Several other conditions on the trunk can mimic acne vulgaris which should be included in the differential diagnosis. History and physical exam are important in order to differentiate these conditions

Malassezia (Pityrosporum) folliculitis

A benign condition that results from the overgrowth of Malassezia yeast present in normal cutaneous flora. Presents as intensely pruritic, 1-2mm, monomorphic papules and pustules on the chest, upper back, and shoulders. The absence of comedones and often pruritic nature of the lesions can help to differentiate pityrosporum folliculitis from acne vulgaris.

Hot tub folliculitis

Folliculitis due to pseudomonas aeruginosa occurring 6 hours to 5 days after exposure to a hot tub. It presents as 2-5mm papulovesicular lesions on an erythematous base. Some vesicles develop pustular apices. The rash is present on the trunk and limbs, usually sparing the face and neck. It is often pruritic and about half of people have systemic symptoms including weakness, myalgia, chills, and fever.4

Steroid folliculitis

A folliculitis that presents as early as 2 weeks after initiation of systemic glucocorticoids or after prolonged use of topical or inhaled glucocorticoids. These lesions are normally all in the same stage of development (small pustules or red papules) and appear mainly on the trunk, which is in contrast to acne vulgaris which usually has involvement of the face. Treatment consists of stopping the steroid.5

Drug-induced acne

Several medicines can cause a monomorphic, diffuse papular eruption that mimics steroid folliculitis. These drugs include some anticonvulsants, isoniazid, halogenated compounds, and some chemotherapy drugs. Treatment consists of stopping the offending agent.5

Occupational acne

Several groups of industrial compounds encountered at the workplace can cause acne. This tends to be very inflammatory and is characterized by large comedones, papules, pustules, large nodules, and true cysts. It also tends to occur on parts of the skin that is normally under clothing. Treatment is to stop exposure. Topical or systemic retinoids or oral antibiotics may be helpful.5

Radiation acne

Acneiform eruption due to ionizing or ultraviolet radiation. This type of acne usually presents as comedo-like papules and can be treated with oral or topical retinoids. 5

Tropical acne

Acneiform folliculitis due to extreme heat. This type of acne mainly occurs mainly occurs on the trunk and buttocks and consists of deep, large inflammatory nodules and often becomes secondarily infected by s. aureus. Treatment consists of oral antibiotics and moving the patient to a cooler environment if possible.5

Acne aestivalis

Monomorphous eruption of multiple, uniform, red, papular lesions after sun exposure, often occurring on the shoulders, arms, neck, and chest. This eruption is due to UVA radiation. This rash will resolve if the patient protects themselves from UV radiation for several months. Topical retinoids and benzoyl peroxide can be helpful to speed up the resolution.5

Steatocystoma multiplex

A rare condition characterized by multiple asymptomatic, yellow to skin colored cystic lesions on the arms, chest, axilla, and neck. When localized to the head and neck, this condition can be confused with acne.6


There is some evidence that sebum excretion plays a smaller role in truncal acne than facial acne. The skin on the trunk differs from facial skin in thickness and has fewer sebaceous glands and a lower pH.2 For this reason, skin on the trunk is likely more affected by clothing and sports equipment causing trapped sweat and oils through occlusion, friction, and pressure.2 Part of truncal acne treatment is education regarding limiting the amount of time spent in sweaty sports gear, or any other clothing that could trap sweat, before cleansing the skin.

Topical Therapy

Treatment of truncal acne is difficult because it often covers a large area with sometimes difficult to reach locations. This limits the utility of topical medications with this type of acne. However, dermatologists should consider topical medications if possible.

Benzoyl Peroxide (BPO) is a potential option, as it is easy to administer to a large area of skin. This is a potent antimicrobial agent that reduces the risk of bacterial resistance to antibiotics and is relatively effective at decreasing the number of acne lesions.2 BPO 5.3% emollient foam has been shown to be superior at reducing P. acnes (the primary bacteria involved in acne) than BPO 8% wash.7 BPO 9.8% emollient foam with a short contact time (2 minutes) can also be used with similar efficacy.8 BPO is a good first line option as there are relatively few side effects. Of note, the medication can cause skin irritation and bleaching of clothing and bedding, which becomes especially problematic when applied to the trunk.2

Topical retinoids and antibiotics may be considered in conjunction with BPO. Neither should be used as monotherapy though, as many studies have shown a much better response when these topicals are combined with topical BPO.1 It should be noted that tretinoin should not be applied at the same time as BPO due to the concern for reducing its effectiveness, as BPO is a strong oxidizer and tretinoin has been shown to be susceptible to this oxidation. While one study suggested that there was actually no BPO-induced degradation of tretinoin when tretinoin gel and BPO gel were used together, the clinical significance of these results are unclear.9 Applying the benzoyl peroxide in the morning and tretinoin at night should avoid the risk for decreased efficacy.10 It should be noted that, however, adapalene is not susceptible to oxidation by BPO.

There was a theoretical concern that application of clindamycin topically to the trunk would result in increased systemic absorption due to the large surface area of treatment. While this concern is largely thought to be false,1 there have been case reports of C. difficile development in patients with long-term topical clindamycin therapy which suggests that rare systemic exposure may occur.11

Other topical medications have had varying degrees of success, including Azelaic acid 15% foam and topical dapsone.2 Azelaic acid is useful as an adjunctive treatment and is recommended in the treatment of post-inflammatory dyspigmentation.12 Topical dapsone 5% gel is useful for inflammatory acne and is particularly useful in adult females.12

Systemic Therapy

Because of the difficulty in applying topical medications, dermatologists often prescribe oral therapies, including oral antibiotics or hormonal therapy.

  1. Systemic antibiotics are effective for the management of moderate to severe acne that is extensive and difficult to treat topically or resistant to topical treatment. Doxycycline and minocycline are first line options, unless the patient is pregnant or a child less than 8 years old. In these cases, oral erythromycin or azithromycin can be used. Bactrim should be limited to patients unable to tolerate tetracyclines or in treatment-resistant patients.12 Oral antibiotics should not be used as monotherapy and their use should be limited to only a few months to prevent the development of antibiotic resistant organisms.2
  2. Hormonal therapy can also be considered as adjunctive systemic therapy for truncal acne. Estrogen-containing combined oral contraceptives are effective for the treatment of inflammatory acne in females. Similarly, spironolactone may be useful in these patients who do not wish to treat with oral contraceptives. Oral corticosteroids can be used temporarily for patients with severe inflammatory acne when starting standard treatment. Low dose oral corticosteroids are recommend only for patients with acne associated with adrenal hyperandrogenism.12
  3. Oral isotretinoin is by far the superior therapy for the treatment of truncal acne. It is recommended as first line therapy for severe nodulocystic and/or scarring acne. It is also recommended for the treatment of moderate acne resistant to other therapies. There are several side effects of this medication, including severe teratogenicity. Females must be on two forms of birth control to take Isotretinoin. Patients must also be counseled on the risks of developing inflammatory bowel disease and depressive symptoms and monitored for the development of these symptoms, although these risks are frequently debated. Most commonly, patients only experience dryness, especially of the mucous membranes. Joint pain is another relatively common side effect. Several early cases described delayed wound healing or keloid formation in patients who were taking or had recently taken Isotretinoin and underwent skin resurfacing procedures, such as dermabrasion or laser resurfacing. Recent studies have not shown any increased risk for atypical scarring, though these procedures should be delayed for 6-12 months after Isotretinoin treatment whenever possible given this potential risk for scarring.12

Alternative Therapies


Acne lesions are often colonized by Propionibacterium acnes (P.acnes), a gram positive bacteria that colonize human skin, especially in pilosebaceous follicles. In vitro studies have shown the capacity of probiotics, such as Streptococcus salivarius and Enterococcus Faecalis, to directly inhibit P. acnes growth. Probiotics therefore have the potential for treating acne through inhibiting P.acnes growth and by decreasing the inflammatory response.13


1) Dihydrotestoerone inhibitors

Physiological adaptation to stress may be a contributing factor to acne vulgaris due to the resulting hormonal cascade. Specifically, physiological stress results in release of corticotrophic-releasing hormone (CRH) which stimulates adrenocorticotrophic hormone (ACTH) release from the anterior pituitary. ACTH stimulates adrenal androgen secretion, while CRH inhibits the release of gonadotrophic releasing hormone. This results in an increased androgen:estrogen ratio, which is an imbalance often seen in acne vulgaris. Dihydrotestosterone (DHT) is produced in the adrenal gland from testosterone by 5 alpha-reductase due to ACTH stimulation. Therefore 5 alpha-reductase inhibiting herbs prevent the formation of DHT. Herbs that act as DHT inhibitors include: Rhodiala rosea, Panax ginseng, Withania somnifera, and G. lucidums and its active phytoconstituent ‘ganoderol B.’

2) Antimicrobial herbs

These herbs work through their primarily bactericidal properties. This includes 5% Tea tree oil, Kaemferol, ethanol extract of H. indicus, C. fenestratum, T. perpurea, E. hirta, E. alba, S. recemosa and C. pepo, Oregon grape crude root extracts, Honokiol and magnolol, and Thai basil oils.

3) Anti-inflammatory herbs

C. acnes stimulates the immune system, leading to the activation of many enzymes and biologically active molecules involved in the development of inflammatory acne. A secreted peptide of P. acnes has also been reported to stimulate the production of pro-inflammatory cytokines, including IL-1, IL-8 and TNF-alpha. Coptis chinensis, Berberis vulgaris, Berberis aristate are herbs that inhibit TNF-alpha pathways. Fruit and rootAngelica dahurica has anti-inflammatory, analgesic, and antimicrobial effects due to the presence of phytoconstituents such as imperatorin, phellopetrin, xantoroxin, byakangelcol, oxypeucedanin, neobyakangelcol and coumarin. Angelica dahurica can also exert anti-inflammatory effects via suppression of neutrophil chemotaxis as well as through other pathways. The ethanol extract ofSelagenella involvens is useful for treating acne through its nitric oxide scavenging effect and inhibition of proinflammatory cytokines. Flavonoids from the plant of Scutellaria radix are also good anti-inflammatory agents.

4) Antioxidant herbs

In acne, reactive oxygen species (ROS) may be released from damaged follicular walls. This is thought to play a large role in the progression of the inflammation involved in acne’s pathogenesis. Drugs that decrease ROS can be helpful in the treatment of acne for this reason. Herbs that decrease ROS include Indian herbs such as Rubia cordifolia, Curcuma longa, Hemidesmus indicus Sphaeranthus indicus, Azadiracta indic, and various Thai medicinal plants.


Many studies show an association between adult acne and a Western diet (rich in animal products and fatty and sugary foods), as well as diets high in milk in high-glycemic index foods.15–20 A healthier diet may be beneficial to the patient for other reasons as well, such as improvement in cardiovascular health. Thus, recommending an elimination diet may not be as beneficial as recommending a healthier, more balanced diet, rich in fruits and vegetable and low in milk and high-glycemic index foods.

Practical Tips

  1. Truncal acne is extremely common and often goes unnoticed and untreated.
  2. Many skin conditions can mimic truncal acne so careful examination and consideration of other disease processes is important when diagnosing truncal acne.
  3. Treatment of truncal acne is similar to treatment of facial acne, but the large surface area and often difficult-to-reach locations often make topical medications less desirable.
  4. For mild truncal acne, consider starting with topical BPO. If resistant, consider adding another topical medication (such as a topical retinoid or antibiotic) in conjunction with BPO. Be sure to warn the patient of the risk of bleaching clothing and bedding when using BPO.
  5. For moderate truncal acne (or mild acne with difficult to reach back involvement), consider adding a systemic medication. Oral doxycycline or minocycline are first line. Hormonal therapy can be used in females.
  6. For severe and/or scarring truncal acne, oral isotretinoin is the treatment of choice.
  7. Consider alternative therapy if patient desires. A healthy diet can be recommended.

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