Sunburn

Acute cutaneous inflammatory reaction to excess ultraviolet radiation, mainly UVB (290 to 320 nm) with a contribution from UVA. Injury to keratinocyte DNA triggers apoptosis ("sunburn cells"), release of inflammatory mediators (prostaglandins, cytokines, histamine) and vasodilatation.

• Time course: erythema starts 2 to 6 hours after exposure, peaks at 12 to 24 hours, and fades over 3 to 7 days, followed by peeling and tanning. Severe burns blister.
• Risk factors: fair skin (Fitzpatrick I and II), outdoor work and recreation, reflective surfaces (water, sand, snow), high altitude, midday exposure, low latitude, ozone depletion, tanning beds, and photosensitising drugs (doxycycline and other tetracyclines, thiazides, amiodarone, fluoroquinolones, NSAIDs such as naproxen, retinoids, St John's wort, voriconazole, and psoralens) and plants (limes, parsley and celery in contact).
• Importance: repeated sunburns, especially blistering burns in childhood, raise the lifetime risk of melanoma and other skin cancers. Five or more sunburns in life roughly double the risk of melanoma.
• Cloud cover transmits up to 80% of UV, so sunburn occurs on overcast days.

• First degree: painful red, warm, tender skin with mild oedema, followed by peeling at 3 to 7 days.
• Second degree: tense blisters on a red base, severe pain, and swelling.
• Systemic features (extensive burn, "sun poisoning"): fever, chills, nausea, headache, dizziness, tachycardia, dehydration, and, in severe cases, hypotension and collapse.
• Eye involvement (photokeratitis): severe pain, tearing, photophobia and grittiness 6 to 12 hours after exposure.
• Lip involvement is common. Burns of the scalp, ears, nose and shoulders predominate.
• Red flags: blistering over more than 10% of the body surface area (for an adult) or more than 5% in infants and children, signs of shock, confusion, high fever, infection, a photosensitising drug, or burns in an infant.
• Differential diagnosis: thermal burn, drug photosensitivity, phototoxic plant reaction (phytophotodermatitis), polymorphic light eruption, lupus erythematosus, porphyria, cellulitis, and heat illness.
• Complications: dehydration, secondary infection, post-inflammatory pigmentation, photoageing, actinic keratoses, melanoma and non-melanoma skin cancer.

• Clinical. Record the extent of body surface involved, depth, exposure history, skin type, drugs taken, and symptoms of systemic illness.
• For systemic burns check core temperature, pulse, blood pressure, hydration, electrolytes, urea and creatinine.
• Swab blisters only if infection is suspected.
• Examine eyes with fluorescein under a blue light if photokeratitis is suspected.

• Move out of the sun, and cool the skin with cool (not ice cold) water showers or cool compresses for 10 to 15 minutes, several times daily.
• Analgesia and anti-inflammatory treatment, started early because they have the greatest effect in the first 24 hours:
  • Ibuprofen 400 mg orally 8 hourly with food (maximum 1.2 g per day without supervision), or naproxen 500 mg orally 12 hourly. Child ibuprofen 5 to 10 mg/kg 6 to 8 hourly. Use with caution in renal impairment, peptic ulcer disease and dehydration.
  • Paracetamol 1 g orally 6 hourly (maximum 4 g per day) if NSAIDs are unsuitable (child 15 mg/kg 6 hourly).
  • Aspirin is not given to children.
• Topical care:
  • Aloe vera gel, cool moisturisers (fragrance free emollient with or without 1% menthol), and cool compresses.
  • A topical corticosteroid (hydrocortisone 1% or mometasone furoate 0.1% once or twice daily for 2 to 3 days) may reduce discomfort if used early, though evidence is limited.
  • Avoid topical anaesthetics containing benzocaine or lidocaine (sensitisation), petroleum jelly and butter on fresh burns (they trap heat), and perfumed products.
• Fluids: encourage oral fluids to replace losses, and give oral rehydration solution or IV 0.9% sodium chloride 1 L over 1 hour (child 20 mL/kg) for dehydration or hypotension.
• Blisters: leave intact. Aspirate large, painful blisters with a sterile needle at the edge and leave the roof as a natural dressing. Apply a non-adherent silicone or hydrocolloid dressing, and keep clean. If the roof is torn, trim away the dead skin and apply a non-adherent dressing.
• Severe burns: prednisolone 0.5 mg/kg per day (30 to 40 mg) for 3 to 5 days, started within the first 24 to 48 hours, is used by some clinicians (evidence limited). Admit for extensive blistering (more than 10 to 15% of body surface area), systemic collapse, or burns in infants.
• Nausea and vomiting: ondansetron 4 mg orally or IV 8 hourly.
• Infection: flucloxacillin 500 mg orally 6 hourly for 5 to 7 days (child 12.5 to 25 mg/kg 6 hourly) for cellulitis, with silver sulfadiazine 1% cream reserved for open burns under specialist advice.
• Photokeratitis: cold compresses, lubricating eye drops (hypromellose 0.3% hourly), cycloplegic (cyclopentolate 1% twice daily) and oral analgesia, with a topical antibiotic (chloramphenicol 0.5% eye drops 4 times daily for 3 days) for large epithelial defects. Healing takes 24 to 72 hours. Refer if there is no recovery in 48 hours.
• Stop or substitute photosensitising drugs where possible, in discussion with the prescriber.
• Prevention:
  • Avoid sun between 10 a.m. and 4 p.m., seek shade, and wear a wide brimmed hat, UV-protective sunglasses and tightly woven clothing.
  • Broad spectrum sunscreen SPF 30 or more (SPF 50 for fair skin and high risk exposure), applied 15 to 20 minutes before exposure at about 2 mg/cm2 (about 35 mL, or 6 teaspoons, for a whole adult body), and reapplied every 2 hours and after swimming or sweating. Use a water resistant product.
  • Avoid sunbeds. Infants under 6 months should be kept out of direct sun, with clothing and shade rather than sunscreen where possible.
• Special groups:
  • Infants and children: ibuprofen or paracetamol by weight, a low threshold for admission, and strict avoidance of aspirin.
  • Pregnancy: paracetamol, cooling and emollients. Avoid NSAIDs in the third trimester, and avoid oral steroids unless essential.
  • Elderly and renal impairment: avoid NSAIDs, and monitor hydration.
  • Photosensitising drugs: counsel on sun protection and review the need for the drug.
• Follow up: most burns resolve in 3 to 7 days. Review in 48 hours for blistering, signs of infection, or persistent systemic symptoms. Advise annual skin checks, and refer for skin cancer screening to dermatology in those with repeated blistering burns, many moles, or a family history of melanoma.