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Last Updated on October 4, 2023
You may have noticed that when you have a laptop computer on your lap, your legs can get very warm.
Working, reading, or playing computer games with your laptop resting on your lap or knees could lead to permanent discoloration of the upper legs after prolonged use.
This discoloration is a condition known as erythema ab igne, or toasted skin syndrome.
Furthermore, research suggests patients with erythema ab igne may carry a long-term risk for developing other malignant skin conditions, such as cancer.
What is Toasted Skin Syndrome?
Toasted skin syndrome is a mottled brownish skin discoloration that results after prolonged exposure to heat radiation, and can occur through laptop use. Under a microscope, Toasted Skin Syndrome resembles skin damaged by long-term sun exposure, and can be very long-lasting.
What Causes Toasted Skin Syndrome?
Laptops give off heat, which is generated by the optical hard drive or the battery, or dispersed by the cooling fan in an effort to keep the computer cool to prevent it from overheating and malfunctioning.
This heat is typically radiated out through the base of the laptop, and because air circulation under the device is restricted, heat can build up on the exterior of the laptop case. Because laptops have optical hard drives located on the left-hand side of the device, computer-induced burning to the skin typically occurs on the left leg. According to the researchers, even mild to moderate levels of heat (109.4 – 116.6°F) can burn the skin, but temperatures of 111.2°F and above can result in toasted skin syndrome.
It is hypothesized that heat exposure may induce damage to superficial blood vessels. This in turn may lead to dilation and deposition of hemosiderin, an iron-storage complex found naturally within cells, which may form a network-like distribution. The result is not pretty. Lesions can begin as transient net-like redness that gradually darkens over time. With chronic heat exposure, the lesions from erythema ab igne can become atrophic, hyper-pigmented, or ulcerated with scaling and widening of blood vessels. Luckily, for most, lesions are typically just ugly and unaccompanied by other symptoms. However, for the unfortunate few, burning and severe itching have been also reported in some individuals.
Researchers stress that the incidence of toasted skin syndrome is likely to increase in the future due to the growing popularity of laptops and iPads. A child’s skin is likely to be more heat sensitive than that of an adult, which is something that parents should consider when purchasing computers for their children.
While some manufacturers, such as Apple, Dell and Hewlett Packard, include warnings of the dangers of using a laptop on the lap in their user-guides, some researchers assert that all laptops should carry warning labels. However, the condition is preventable by placing heat protection between the laptop base and the user’s body.
Case Studies of Erythema Ab Igne
Ryan R. Riahi MD and Philip R. Cohen MD published a paper, called Laptop-induced erythema ab igne: Report and review of literature. In this paper, they review case studies and consolidate worldwide literature on the skin condition erythema ab igne.
In one occurence, Dr. Kimberley Salkey treated a student with a strange skin condition, but wasn’t sure what it was. After questioning, the student shared that he used a laptop computer in his lap for up to 6 hours a day. When tested, the temperature underneath the computer was measured at 125º Fahrenheit. The student’s skin condition turned out to be Toasted Skin Syndrome.
Swiss researchers Dr. Andreas Arnold and Dr. Peter Itin reported the case of a 12-year-old boy who developed a strange discolored patterning on his thigh after prolonged use of his laptop while it was resting on his lap. The boy, who acknowledged that he felt a high level of heat discomfort on one side whilst using the laptop, developed the condition after he had played computer games for just a few hours a day over several months. He was the youngest case at the time the study was conducted.
A 21-year old woman went to the clinic after noticing a gradual development of net-like hyperpigmentation on her legs. She did not take any medications and witnessed no other symptoms. From physical observation of the pattern of the discoloration, it was noted that more hyperpigmentation occurred on her left thigh rather than her right.
Credits: Dermatology Online Journal, UC Davis
Further investigation revealed that the pattern of discoloration correlated with the laptop position, which the woman used to hold her computer on her thighs. As a college student, she would sit with her laptop on her thighs for prolonged periods of time to do school work.
Having spent some time in the clinic, doctors evaluated the pattern and distribution of the skin discoloration. They also questioned the patient as to her normal behaviors. They looked into her past and present medical history. The patient had no other known skin conditions and was not taking medication. As the lesion borders were consistent with the position of the laptop on her thighs, doctors concluded that this was indeed a confirmed case of erythema ab igne.
Credits: Dermatology Online Journal, UC Davis
Consequently, the patient was advised to stop using laptops on her thighs. Subsequent follow-up visits were scheduled to review the prognosis of the condition. Although the patient did stop using the laptop on her legs, doctors found that the skin lesions remained hyper-pigmented. Furthermore, the hyper-pigmentation remained localized to where her laptop had been. There was no decrease or increase in the severity of pigmentation after the laptop use was discontinued but the blotchiness of her skin remained. Her skin did not revert back to its normal state.
All patients studied reported having lesions on the upper part of either one, or in some cases both legs, which developed after using a laptop for between 6-8 hours a day over several weeks or months.
You may wonder how people can possibly develop skin rashes without noticing. Erythema ab igne is not immediately noticeable as it is a chronic condition, which takes time to become visible.
How to Prevent Toasted Skin Syndrome
In mild cases the mottled discoloration is temporary and typically causes no other side effects, although some patients reported an itching or burning sensation.
However discoloration can become permanent with prolonged use, and can develop into burns when temperatures are high enough.
Although the chances of the condition developing into skin cancer are low, doctors recommend that patients with extensive skin damage should be closely monitored. To prevent toasted skin syndrome, it is suggested to limit using a laptop directly on the lap or to take preventative action by using a laptop heat shield to minimize contact to the heat source.