Sometimes patients think that I am just making up diagnoses. This is a classic example.
I had a patient yesterday who had seen several physicians for evaluation of this strange rash on her back. She had had it for months. It didn’t hurt. It didn’t itch. It hadn’t changed. She and her husband were concerned by its appearance and by the fact that her doctor didn’t know what it was.
I took a look at her and asked one question to make the diagnosis.
“Do you use a heating pad?”
“No,” she replied, wrinkling her brow at my curious question. “Why would a heating pad cause a rash anyway?” She asked.
“It’s not the pad,” I answered, “It’s the heat.”
“Well, I do sit by the fireplace on cold nights,” she added.
“Eureka!” I exclaimed. (Well, actually I didn’t, but I thought it). “Do you sit with one side to the fire?”
“Yes, I sit with my left side to the fire while I read.”
“You have erythema ab igne,” I said.
“You’re just making that up, right?” she asked.
I’m not. Erythema ab igne, also known as toasted skin syndrome, is a red, brown rash that develops as a result of prolonged exposure to heat without an actual burn. The redness develops in a particular pattern, as seen in the photo, called reticulate or net like. Slowing of blood flow in the affected area, called hemostasis, is likely the cause.
The rash can be various colors from red to pink to brown. It improves after stopping exposure to heat, but in some instances, the brown coloring might be permanent.
Any source of prolonged heat like heating pads, water bottles, even laptop computers (if it sits on your lap) can be a cause. It is well documented in old dermatology books on the legs of women who would sit close to the fire or the pot belly stove in the winter to try to stay warm.
Ironically, my patient lives here in San Diego. Cold nights, as it turns out, are a relative thing.
Related posts:
- Brown Skin Spots Ever notice brown spots on your skin after a...
- Skin Care Myths: It’s Normal for Moles to Change During Pregnancy It is a widely held belief that moles or nevi...
Uncategorized 
Interesting diagnosis. Must have felt good to figure that one out.
Dermatology is such a fun specialty.
Dr. Val,
I love my job.
I had this a few months ago on my thighs from my laptop! Small areas about the size of a palm on my anterior thigh, usually worse after the laptop was used, but it was always present. It finally went away about a month after I bought a lap desk for under my computer. My husband thought I was crazy when I said it was from my hot computer, but I’ll be showing him your post later tonight!
Does anyone else have any experience with this?
I also experienced this from my laptop being on my lap. I was scared so I blocked it out and kept using my laptop unsafely, now a large area on my left leg has this lattice markings in brown. My mother finally pointed it out and made me look it up and face facts, i’m now keeping my laptop away from my body when I use it and hoping with shae butter lotion and B vitamins I can get rid of the skin marks and possible start of nerve damage underneath. This diagnosis is real, and it should be more wide known!
I have stage 4 endometriosis that has recently taken a turn for the wors. I have been using my heating pad and hot water bottle almost continuously for the past 3-4 weeks, even when I was sleeping. The other day I noticed marks like the on in the picture above on my belly and upper thighs and have been quite worried about them. Thanks for clearing up for me what it is. Can you tell me, will it go away? I still really need to use my heating pad but I’m afraid to make the markings permanent. So I’ve just been suffering.
I went to the dermatologist today, and he indicated that I have toasted leg syndrome. I first went to a general physician who prescribed antifungal meds as she thought it was a fungus. When I went to the dermatologist today the physician assistant was already to take a leg scrape/biopsy for testing when the physician came in looked at my leg and asked where do you work? are you exposed to a heater? The answer was yes. He showed me a photo of the condition and sure enough, the pattern on my leg is very similar. It had some pink center and had started turning brown. He prescribed a medication to even my skin tone which is a tough feat with black skin.
I hope i didn’t cause myself any permanent damage.
I just found this while looking up “heating pad burn” because I have this very thing on my back. I hurt my shoulder and it’s been giving me a lot of pain between my shoulderblades. I’ve had a heating pad on the back of my chair 24/7 to be there when I am sitting down for some relief.
I’m relieved to hear it’s not something too serious, but I have stopped using the heating pad for now. I guess sitting with it between my back and the back of the chair on the highest setting for hours on end is not the best idea.
I have the same thing on my leg I stay cold all the time so i sit at my computer with my hair dryer on low lol. I think I should start using a blanket instead.
Ive noticed this same “rash” on my legs for about a month now. It was very light so I just ignored it and chalked it up to poor circulation (even though Im a healthy, active, 36yr old). This morning while I was getting dressed, I noticed my “poor circulation rash” had gotten much MUCH worse. I also noticed a blister on my ankle bone. After spending over an hour researching different symtoms online, and trying not to completely freak out, a light buld went off in my head and realized that the blister was likely to have been caused from my heating pad.I had taken a muscle relaxer last night and fell asleep with the heating pad on. I had put the heating pad on a pillow, and then put my right calf onto of the heating pad, adn fell asleep (I still cant believe I could sustain a burn like that without waking up, scary). Still unsure what the sqiggle red lines all up and down my calf were, I continued to search the web, this time I searched for heating pad burns. Im go grateful I came across this site. My leg looks exactly like the picture shown above. Ive used a heating pad (on my legs) every night for over a year now. My rash had been very faint in both legs for a while, but not enough that I ever gave it much thought. Guess it’s time to invest in some some soft snuggly socks and unplug the heating pad. I really hope this is going to go away, its pretty horrible looking!