Chronic heat dermatitis, hot water bottle rash, fire stains, granny’s tartan, toasted skin syndrome, erythema a calore, ephelis ignealis

Erythema ab igne (from Latin language, meaning  “redness from fire”) is a localized, reticular, pigmented, asymptomatic  dermatosis due to prolonged, repeated, long-term  exposure to head (low levels of infrared thermal radiation in the range of 43-47°C, insufficient to produce a direct burn).
It was first described in the United Kingdom from a London dermatologist, Horatio George Adamson, associated with the use of peat stoves. A german dermatologist, Abraham Buschke, in the early 1990s gave the name “Hitze melanose,”, which means melanosis induced by heat.
Initially, the skin shows a mild, transient macular erythema in a reticulated pattern that in size and shape often approximates that of the heat source; with repeated exposures, the erythema persists evolves into a brown reticulated hyperpigmentation.

It was once a common condition seen on the anterior shins of elderly who stood or sat too closely to wood-burning  stoves or open fires. Localized lesions seen today reflect the different sources of heat that people may be exposed to:

• Heat pads
• Hot water bottles
• Electric stoves/heater
• Open fires
• Space heaters
• Coal stoves
• Peat fires
• Wood-burning stoves
• Steam radiators
• Hot stoves
• Sauna belts
• Car heaters
• Heated reclining chairs
• Heated popcorn kernels
• Heating blanket
• Hot bricks
• Infrared lamps
• Microwave popcorn
• Laptop computer
• Automobile seat heater

However, once the heat source is identified, it is important to determine if it is being used to relieve pain and, if so, the cause of the pain (erythema ab igne overlies the source of pain). In the differential diagnoses must be considered:

• Cutis marmorata
• Livedo reticularis
• Livedoid vasculitis
• Poikiloderma atrophicans vasculare
• Poikiloderma vasculare atrophicans (parapsoriasis variegata)

About the pathogenesis, it has been proposed that thermal radiation exposure can induce epidermal damage to superficial blood vessels (the superficial subcutaneous plexus found in the papillary dermis) that subsequently leads to vascular dilation. The vasodilation of vessels presents morphologically as the initially observed erythema. Red blood cell extravasion and deposition of hemosiderin that follows clinically appears as hyperpigmentation. It has also been proposed that the distribution of affected blood vessels results in the net-like pattern of erythema ab igne skin lesions.

The initial treatment of erythema ab igne is discontinuation of the contact with the heat source. If the area is only mildly affected with slight redness and little or no pigmentary changes, the condition may resolve by itself over a few months. If the skin is pigmented, resolution is unlikely and may persist for years. Treatment with topical tretinoin or lasers may improve the appearance.