Skin problems on the trunk

Author: Hon Assoc Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, September 2015.

Links to pages about skin conditions that favour the trunk.

Trunk: erythema without surface change

Erythema is less pronounced in dark skin.


  • Intermittent redness eg when hot, embarrassed or with certain foods
  • Often lifelong tendency
  • Systemically well
  • May precede/accompany rosacea


  • Sun-exposed site
  • Painful
  • Consider phototoxic drugs


  • Weals can arise on any site
  • Spontaneous and inducible types

Trunk: red papules/pustules

Acne vulgaris

  • Upper trunk
  • Open and closed comedones
  • Nodules + cysts if severe

Hot tub folliculitis

  • Bathing costume distribution
  • Exposed to hot tub
  • Papulopustules
  • Rarely, fever

Lichen planus

  • Lower back
  • Firm, violaceous papules + white streaks
  • Favours areas of earlier injury
  • Also examine mouth, distal limbs

Malassezia follicultiis

  • Upper trunk
  • Monomorphous superficial papulopustules


  • Mid trunk
  • Acute non-follicular papulopustules
  • Follows heat/sweating

Morbilliform drug eruption

  • Entire trunk spreading to limbs
  • Commenced new drug within 10 days
  • Monomorphic macules and papules
  • Variable itch

Trunk: erosions/crusting

Herpes zoster

  • Dermatomal
  • Painful
  • Erythema may precede vesicles
  • Culture/PCR: Herpes varicella zoster


Scabies rash

  • Burrows between fingers, wrists
  • Nodules in axillae, groin
  • Intense itch, especially at night
  • Dermatoscopy of burrow reveals mite

Transient acantholytic dermatosis / Grover disease

  • Acute or chronic
  • Itchy or asymptomatic
  • Elderly males
  • Crusted papules


  • Febrile illness
  • Also involves face, oral mucosa
  • Monomorphic eruption
  • Culture/PCR: Herpes varicella zoster

Trunk: dry/scaly + very itchy

May also blister, swell.

Allergic contact dermatitis

  • Acute flares on any site
  • Asymmetrical, odd-shaped patches/plaques
  • Patch tests positive

Atopic dermatitis

  • Patchy or diffuse
  • Acute flares are erythematous
  • Chronic eczema is lichenified

Nummular dermatitis

Secondary syphilis

  • Rash involves palms, soles
  • Positive syphilis serology

Trunk: dry and scaly with minimal itch

Annular erythema

  • Slowly enlarging rings
  • Scale just inside periphery

Pityriasis rosea

  • Distribution along Langers lines (fir tree pattern)
  • Larger herald patch appears several days before others
  • Oval shaped plaques with scale just inside periphery
  • Variable itch

Pityriasis versicolor

  • Mid-upper back and mid chest
  • Pale, pink or brown macules, patches
  • Diffuse bran-like scale
  • Mycology microscopy negative, culture positive


  • Roughly symmetrical distribution
  • Well-circumscribed erythematous scaly plaques
  • Variable itch

Seborrhoeic dermatitis

  • Mid-upper back and mid chest
  • Erythema, flaking
  • Skin feels rough on palpation
  • Often, follicular prominence

Subacute lupus erythematosus

  • Upper trunk
  • Thin erythematous plaques
  • Peripheral scale
  • Check CBC, ANA, ENA
  • Biopsy confirmatory

Tinea corporis

  • Asymmetrical annular or discoid shaped plaques
  • Peripheral scale
  • Mycology microscopy + culture positive

Trunk: multiple skin coloured papules

Comedonal acne

  • Open and closed comedones
  • Folliculocentric

Granuloma annulare

  • Arranged in rings

Steatocystoma multiplex

  • Genodermatosis
  • Superficial pseudocysts

Pigmentary changes

Pigmentation is more pronounced in dark skin.

Postinflammatory pigmentation

  • Preceding eczema, psoriasis, acne etc
  • Distribution depends on cause

See also pigmentary disorders

Contribute to Dermnet

Did you find this page useful? We want to continue to deliver accurate dermatological information to health professionals and their patients — for free. Funding goes towards creating articles for DermNet, supporting researchers, and improving dermatological knowledge around the world.

Donate now with credit card or Paypal


Related information


Books about skin diseases:

See the DermNet NZ bookstore