Erythema Ab Igne: Causes, Symptoms, and Treatment

Medically Reviewed by Zilpah Sheikh, MD on May 02, 2024
6 min read

If you use a heating pad regularly, you might notice a rash in that area. This is erythema ab igne, also known as “EAI,” “toasted skin syndrome,” or “fire stains.” 

Erythema ab igne is Latin for “redness from fire.” That’s because this rash is caused by long-term exposure to low heat. It usually starts off as blotchy and pink, then turns into a brownish fishnet pattern.

Erythema ab igne is fairly uncommon. It’s more likely to affect people who regularly use heating pads for chronic pain or who work near heat sources. 

Women and people assigned female at birth are also more likely to get it. In the past, this was because they spent a lot of time near stoves. Back then, it was 10 times more common among women than men. Today, they are still twice as likely to get this rash. It’s especially likely to appear on the front of their legs. 

This rash can happen at any age. But on average, people get it when they’re 28 years old.

It’s caused by being near a heat source for too long. It doesn’t have to happen all at once. The rash can come from weeks or years of repeated exposures. The heat isn’t hot enough to burn you right away, but over time, it causes damage. This happens in temperatures less than 45 C or 113 F.  

Heat damages the skin’s surface and blood vessels, causing them to expand and become inflamed. This leads to redness. Over time, it also causes the deposition of chemicals like hemosiderin (a brown molecule that carries iron) and melanin (the dark-colored molecule that plays a role in skin, hair, and eye color), turning your skin a reddish-brown. The skin damage can lead to changes in skin thickness or blistering.

In the past, erythema ab igne mainly happened to people who worked near stoves or fires, like bakers and metalworkers. Central heating has made it less common because people don’t spend as much time near heat stoves or coal fires. Today, it is often caused by exposure to laptops (and other electronics), space heaters, heating pads, and heated seats in cars. 

This rash is famous for its fishnet pattern. It appears where the heat source warmed your skin. For example, this could be where you use a heating pad on your lower back or rest your laptop on your stomach.

At first, the rash is blotchy and pink. If you press it, the area will stay white or pale for a few moments. This is a sign of interrupted blood flow.

Over time, it becomes red, purple, or brown. If you touch the rash in this stage, it no longer stays white or pale. 

At this stage, the rash has a lace-like pattern, mimicking the network of blood vessels in the outer skin layer. The skin may also become thinner or thicker and could develop blisters.

Some parts of the rash change color and shape faster than others, so you might have a mixture of pink patches and brown lines.

Usually the rash isn’t bothersome, but sometimes it can be itchy, burning, or painful.

This rash can look like other conditions or make it harder to spot other conditions, so it’s important to talk about it with your dermatologist (a skin doctor). They can help you figure out what it is and what caused it.

Similar rashes can be caused by:

  • Livedo reticularis
  • Basal cell carcinoma and other skin cancers
  • Colonic adenocarcinoma
  • Vasculitis
  • Dermatomyositis

The main difference is that erythema ab igne is caused by heat exposure.

The doctor will look at the rash and ask questions. By itself, a mild case of erythema ab igne is usually harmless, but sometimes it can be a sign of chronic inflammation. Your doctor might ask if you’re using a heating pad to treat chronic pain or if you have a healthy relationship with electronics. They might also suggest tests to rule out other conditions. This can help them figure out and treat the root of the problem.

They also might ask for a skin biopsy. This is when they take a tiny piece of skin and look at it under the microscope. They’re looking at the skin cells to make sure there’s no signs of cancer.

The most important thing is to avoid the heat source. This will stop the rash from getting worse and give it time to get better. It might mean putting your laptop on a desk instead of your legs, or not using the seat warmers in your car. 

If you have chronic pain, talk to your doctor about how to manage it without a heating pad. For example, you could try medicines or acupuncture. 

If your job involves heat (like if you’re a baker), talk with your doctor about ways to manage this exposure. You can request reasonable accommodations under the Americans With Disabilities Act. This means that you can ask your job for small changes, like working farther away from a heat source or using protective gear. As long as they don’t interfere with your job, these changes should be fine.

Mild rashes will usually go away on their own within a few months, although it sometimes can take years. In rare cases, the rash could cause scarring.

If you’re upset by how the rash looks, you can try creams with 5-fluorouracil, tretinoin, or hydroquinone. You could also try laser therapy. These might help with skin discoloration caused by erythema ab igne. Creams with 5-fluorouracil might also help prevent the rash from becoming cancerous. When using these medications, take precautions and consult a dermatologist first, especially if you are unsure about the application or potential side effects.

Rarely, this rash can lead to skin cancers like squamous cell carcinoma (SCC) or Merkel cell carcinoma. This can happen decades after the rash first appears. Your dermatologist will keep an eye on your rash and how it heals. If it doesn’t go away, they might suggest a skin biopsy to check for cancer.

They also might prescribe 5-fluorouracil cream. Some studies suggest that it might help prevent the rash from turning into SCC, but more research is needed to be sure.

The main way to prevent this rash is to avoid spending too much time near heat sources like laptops, heating pads, and stoves. Limit how often and how long you use these items. 

If you use a heating pad for chronic pain, talk to your doctors about other treatments. They might suggest medicine, acupuncture, or other therapies.

If you work near stoves or other hot machinery, talk to your doctor or manager about ways that you can protect yourself on the job. This could mean avoiding hot ovens or wearing protective equipment. 

Erythema ab igne is a rash caused by long-term exposure to low heat. It starts off as pink blotches before developing into a brown fishnet pattern. 

The main way to treat it is limiting exposure to heat sources like heating pads and laptops. It should get better on its own in a few months, but in rare cases could lead to skin cancer.

Does erythema ab igne go away? 

It usually goes away on its own within a few months. In rare cases, it could cause scarring.

Should I see a doctor for erythema ab igne? 

It’s important to see a skin doctor, or dermatologist, for any unusual rash. Erythema ab igne can look like many other conditions, including skin cancer. A dermatologist can help figure out what is causing your rash and how to treat it.

Is toasted skin syndrome serious?

It’s usually harmless, but in rare cases it could lead to skin cancer.

Is erythema ab igne cancerous? 

The rash itself is not usually cancerous, but in rare cases, it can turn into skin cancer. This can happen decades after the rash first appears. A dermatologist can look for any signs of skin cancer.