logo Photosensitivity

Miscellaneous dermatology

Photosensitivity

Objectives

  • Recognise photosensitivity and distinguish common variants.
  • Provide advice about photoprotection.

Introduction

The term photosensitivity describes an abnormal response of the skin to light, occurring within minutes to weeks of exposure and lasting for minutes to months.

Photosensitivity may result in phototoxic sunburn-type response or a variety of idiopathic or photoallergic rashes.

Distribution involves areas exposed to the light, predominantly face, neck, V of neck, backs of hands, lower legs and tops of feet. Unaffected areas include:

Precise diagnosis can be difficult and requires a careful history.

Broadband phototesting

UVA-induced erythema

Results of monochromator testing


Sunburn

Sunburn is maximal about eight hours after exposure to ultraviolet radiation from sunlight or artificial sources (predominantly UVB). Features include:

Sunburn arises with less exposure to sunlight when the patient is taking phototoxic drugs (sulphonamides, thiazides, tetracyclines, phenothiazines, nalidixic acid, amiodarone, naproxen and psoralens). Consider systemic lupus erythematosus in the differential diagnosis.

The histology is characterised by ‘osunburn’ cells (apoptotic keratinocytes), lymphocytic exocytosis, vacuolisation of melanocytes and endothelial swelling of blood vessels.

Prevention of sunburn requires the use of covering clothing, sunscreens and perhaps oral antioxidants such as Polypodium leucotomas. Treatment may consist of rest, fluid replacement, cooling wet dressings, topical steroids and NSAIDs.

Acute sunburn

Peeling from sunburn

Chlorpromazine phototoxic reaction


Photocontact dermatitis

Photocontact dermatitis (eczema) refers to dermatitis arising from contact with a photoactive chemical when exposed to light.

Pigmentation due to topical psoralens photosensitisation

Vesicular eruption due to sunscreen

Coal tar and UV is effective treatment for psoriasis


Phytophotodermatitis

Wild carrot

Acute string trimmers’ dermatitis

Persistent pigmented macules

Berloque dermatitis


Drug-induced photosensitivity

Drug-induced systemic photoallergy have various patterns most often eczematous dermatitis or a lichenoid eruption (i.e. having histological features similar to lichen planus). Photosensitivity affecting the nails results in lifting of the nail plate off the nail bed (photo-onycholysis) and may take many months to recover.

Eczematous drug-induced photosensitivity (NSAID)

Lichenoid drug-induced photosensitivity (quinidine)

Photo-onycholysis (doxycycline)


Photo-aggravated dermatoses

Photo-aggravated dermatoses include:

Management involves treating the underlying disease and photoprotection

Photoaggravated Darier’s disease

Pellagra

DSAP


Polymorphous light eruption (PMLE)

Polymorphous light eruption (PMLE) is a common idiopathic photosensitivity eruption affecting young adult women. Features include:

PMLE should be managed by sun protection, with a gradual increase in exposure. Some patients find antioxidants such as beta carotene or Polypodium leucotomas of benefit. Severe cases may be referred to a dermatologist. Treatment options include:

Typical papulovesicles

Erythematous macules and plaques

Eczematous plaques

Juvenile spring eruption


Rare idiopathic photodermatoses

Rare idiopathic photodermatoses include:

Actinic prurigo

Actinic reticuloid

Solar urticaria


Photoprotection