Erythema ab igne
Also known as toasted skin syndrome or ephelis ignealis
What is erythema ab igne?
Erythema ab igne (EAI) is a skin reaction characterised by a pattern of erythema (redness) resembling a net or hyperpigmentation (increased pigmentation) caused by chronic exposure to heat. In the past, EAI most commonly affected people who spent excessive time in front of stoves, open fires and space heaters. Although central heating has significantly decreased the incidence of EAI, it still affects people with occupational exposure to fires, people who use heat packs and those with medical conditions associated with decreased sensation.
What causes EAI?
Chronic exposure to heat below the threshold for a thermal burn (ie below 45OC) is the primary cause of EAI. The exact way EAI develops is unclear but the pattern associated with the condition corresponds with the blood vessels of the skin.
What does EAI look like?
In the early stages, there may be a temporary redness in a pattern resembling a lacework or fishing net. This fades easily when pressed. After chronic exposure to heat, the redness network becomes fixed and does not fade. Later-stage lesions may show atrophy (thinning of the skin), become scaly and blisters may appear.
There are usually no other symptoms associated with EAI but some people may experience a burning sensation or itchiness.
The location, size and shape of the lesions are often associated with a particular heat source. For example:
- Lesions on the shin are associated with exposure to heaters, stoves, etc.
- Lesions on the lower back may be associated with the application of hot water bottles or heat packs to manage chronic back pain.
- Lesions may also correspond to occupational hazards, for example, bakers and chefs may have lesions on their arms while glass blowers, silversmiths and jewellers may have lesions on their face.
- Lesions may develop on the thighs of people after prolonged use of laptop computers.
What other problems can occur with EAI?
There is an exceedingly rare association with the development of squamous cell carcinoma in affected areas that can develop 30 years or more after chronic exposure.
How is EAI diagnosed?
A dermatologist usually makes the diagnosis based on clinical features and medical history. Biopsy is not performed unless there is suspicion for malignant change.
How is EAI treated?
Management primarily consists of avoiding the source of chronic heat exposure. Mildly affected areas may resolve in several months. However, severely affected areas that are associated with skin atrophy and pigmentation are unlikely to resolve.
This information has been written by Dr Rose Liu and Dr Deshan Sebaratnam 20/07/2017