Sunburn

See the separate related article Burns - Assessment and Management.

What is sunburn?

Sunburn is a common, acute inflammatory response of skin to exposure to ultraviolet radiation (UVR).

UVR causes vasodilation and release of mast cell mediators, leading to an inflammatory response. Less intense or shorter-duration exposure to UVR leads to increased skin pigmentation (tanning) which provides some protection against further UVR-induced damage.

Sunburn risk factors¹

• Duration of exposure.

• Height of the sun (greatest exposure at midday, in midsummer and at the equator).

• Type of UVR: UVB is more potent than UVA, but less prevalent in sunlight.

• Increasing altitude (less atmospheric filtration).

• Environmental reflection - eg, rippling sea, white sand. Snow and ice can facilitate sunburn with ambient temperatures below zero.

• Lack of protective sunscreen or clothing increases the risk. It is possible to burn through light clothing.

• Lighter skin pigmentation is a factor, whether congenital or acquired. Being suntanned gives protection. Skin type is graded I to VI according to risk of burning.

• Moist skin increases the risk.

• Limb skin is relatively more resistant than that of the face, neck and torso. Areas not habitually exposed are more vulnerable.

• The filtering effect of the atmosphere has an effect. The diminishing ozone layer increases the risk whilst atmospheric pollution reduces it.

• Areas of vitiligo are susceptible to burning, as are areas of alopecia. People with albinism are very sensitive to sunburn.

• Photosensitivity - for example, systemic lupus erythematosus, porphyria; drugs such as tetracyclines and many others. Xeroderma pigmentosum and certain other genetic conditions may cause sunburn with minimal sun exposure, due to defective DNA repair.

• Overuse of sunlamps.

Symptoms of sunburn (presentation)¹

• The skin is hot and red. It blanches on pressure. It is painful and tender and there may be some oedema.

• Erythema usually occurs 2-6 hours after exposure and peaks at 12- 24 hours. It resolves over 4-7 days, usually with skin scaling and peeling.

• With more severe sunburn, vesicles and bullae may form.

• Systemic symptoms can accompany severe sunburn: there may be headache, chills, malaise, nausea and vomiting.

Assessment²

• As for any burn - assess the severity and area covered (see box below).

• Examine the skin for colour change, blisters and capillary refill.

• Assess degree of pain.

• Check for dehydration.

• Look for symptoms/signs of heat exhaustion or heatstroke? For example:
  

  • High body temperature.

  • Fatigue, weakness, dizziness, fainting, headache.

  • Nausea or vomiting.

  • Rapid pulse.

  • Myalgia.

  • Altered behaviour - irritability, agitation, impaired judgement, confusion, disorientation, hallucinations.

• In children (as with any burn) consider whether neglect or non-accidental injury could be a cause.

• Presence of co-existing injuries.

• Note co-existing or contributing medical conditions.

Who needs referral for sunburn?²

Minor burns, including sunburn, can usually be treated in primary care. Superficial epidermal burns do not need referral. The following patients need referral (usually to A&E in the first instance but may be referred to a burns unit, depending on local protocols):

• All deep dermal and full-thickness burns.

• All circumferential burns (those that go all the way round a part of the body).

• Superficial dermal burns of more than 3% total burn surface area (TBSA) in those aged ≥16.

• Superficial dermal burns of more than 2% TBSA in under-16s.

• Superficial dermal burns involving the face, hands, feet, perineum, genitalia or flexures.

• Suspicion of dehydration, heatstroke, shock or sepsis.

• Suspicion of non-accidental injury or neglect.

Referral should also be considered in the following scenarios:

• Young or old: children aged <5 years, adults aged >60 years.

• Co-existing medical problems (eg, cardiac, respiratory or hepatic disease; diabetes; immunosuppressed; pregnancy).

• Needing admission for social reasons, pain control or if dressings are difficult to manage.

• Uncertainty about the depth or severity of the burn.

• Other injuries.

• A wound that has not healed 14 days after injury.

Differential diagnosis

The cause is usually clear from the history, but consider:

• Photosensitivity.

• Xeroderma pigmentosum and related conditions (if there is sunburn with minimal exposure).

• Other types of burn.

• Neglect or non-accidental injury in children.

• Solar burn reactivation: this is a rare and idiosyncratic drug reaction, reported with a variety of drugs, including methotrexate. It affects areas of the body that have been previously sunburned.^{4 5}

Sunburn treatment and management²

Mild-to-moderate sunburn

• The vast majority of sunburn is superficial and spontaneously resolves.

• Maintain adequate hydration.

• Symptoms may be relieved by:
  

  • A cool shower or cool compresses.

  • Simple analgesics (paracetamol or ibuprofen).

  • Emollients.

Moderate

• Treat any dehydration or heatstroke.

• Symptom relief (as above).

• If there are blisters (superficial dermal burn), wound care and dressings are needed. See the separate Burns - Assessment and Management article.

Some sources suggest that oral non-steroidal anti-inflammatory drugs (NSAIDs) and/or topical steroids reduce erythema.¹ However, one small trial and reviews of the literature have been less enthusiastic.⁶ One review found that the overall opinion was that corticosteroids, NSAIDs, antioxidants, antihistamines or emollients were ineffective at decreasing recovery time.⁷ The remaining studies showed mild improvement with such treatments; however, study designs or methods were flawed. Furthermore, regardless of the treatment modality, the damage to epidermal cells is the same. Topical anaesthetics are not recommended.

Severe

Treatment should be as for any other severe burn. See the separate Burns - Assessment and Management article.

Complications¹

• Heatstroke or dehydration.

• Secondary infection of the burn.

• Exacerbation of some dermatological conditions.

• Premature ageing, solar keratoses, basal cell carcinoma, squamous cell carcinoma of skin and malignant melanoma of skin are associated with sun exposure.

• Photosensitivity reactions.

Sunburn prevention^{1 8}

Sunburn is better prevented than treated. Sun protection is the best defence against sunburn and other damaging effects of UVR:

Sunscreen

A sunscreen of at least sun protection factor (SPF) 30 (SPF 50 for children) should be used for sun protection.

The safest advice with regard to how much sunscreen to use is "apply liberally". Different products require different amounts so attempts to suggest a standard formula are confusing and not necessarily accurate.

The SPF protection offered by a sunscreen indicates how many times longer a user can stay in the sun compared with the individual without the sunscreen - eg, a cream with SPF 15 can stay 15 times longer. This is calculated with an application thickness of 2 mg/cm². Unfortunately, sunscreen is very often applied much less than this, typically between 0.5 to 1 mg/cm², giving a sunscreen labelled SPF of 15 a true SPF of 2-4.

Perhaps a better way of thinking about the SPF is that wearing a sunscreen with a given SPF reduces the UV dose to 1/SPF of that which would be received by spending the same time in the sun but with no sunscreen applied - eg, SPF 15 sunscreen results in a UV exposure to the skin of one-fifteenth of that which would be received without any sunscreen.

The degree of protection against UVA is hard to quantify and is usually much less than protection against UVB.

Concomitant use of insect repellents that contain N,N-diethyl-3-methylbenzamide (DEET) also decreases SPF.

Water-resistant sun protection lotions last longer than others but even they get washed off by sweat and swimming and need to be replaced.

The Met Office provides a UV section with their weather forecasts, with advice on appropriate precautions.⁹