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Erythema ab igne

Erythema ab igne is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Erythema ab igne rather than just read about it. In short: Erythema ab igne (Latin for 'redness from fire'), or EAI, also known as hot water bottle rash or toasted skin syndrome, is a skin condition caused by long-term exposure to heat (infrared radiation). Prolonged thermal radiation exposure of the skin can lead to the development of reticulated erythema, hyperpigmentation, scaling, and telangiectasias in the affected area.

Erythema ab igne — main illustration
Erythema ab igne — illustration

Key takeaways

  • Erythema ab igne belongs to physics; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Erythema ab igne to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Erythema ab igne from memory before moving on to harder problems.

Reference excerpt

Erythema ab igne (Latin for 'redness from fire'), or EAI, also known as hot water bottle rash or toasted skin syndrome, is a skin condition caused by long-term exposure to heat (infrared radiation). Prolonged thermal radiation exposure of the skin can lead to the development of reticulated erythema, hyperpigmentation, scaling, and telangiectasias in the affected area. Some people may complain of mild itchiness and a burning sensation, but often, unless a change in pigmentation is seen, it can go unnoticed.

Causes

Different types of heat sources can cause this condition, such as:

Repeated application of hot water bottles, heating blankets, or heat pads to treat chronic pain—e.g., chronic back pain. Repeated exposure to heated car seats, space heaters, or fireplaces. Repeated or prolonged exposure to a heater is a common cause of this condition in elderly individuals. Occupational hazards of silversmiths and jewelers (face exposed to heat), bakers, and chefs (arms, face) Resting a laptop computer on the thigh (laptop computer-induced erythema ab igne). In a 2012 review, Riahi and Cohen describe the characteristics of laptop computer-induced erythema ab igne. Temperatures between 43 and 47 °C can cause this skin condition; modern laptops can generate temperatures in this range. Indeed, laptops with powerful processors can reach temperatures of 50 °C when in operation and be associated with burns. Positioning the laptop on the thighs can allow for direct exposure to the heating elements of the laptop, which include the central processing unit (CPU) and the graphics processing unit (GPU). At least 15 cases have been reported by 2012 with the condition usually affecting the left anterior thigh. In these reports, 9 of the 15 patients were women (60%) with an average age of 25 years at diagnosis. In Kashmir, due to the use of a kanger, which also causes kangri cancer. It is a classic finding in chronic pancreatitis and may also be seen in people with hypothyroidism or lymphedema

Pathogenesis The pathogenesis of erythema ab igne remains unknown. It has been proposed that thermal radiation exposure can induce damage to superficial blood vessels that subsequently leads to epidermal vascular dilation. The dilation of vessels presents morphologically as the initially observed erythema. Red blood cell extravasation and deposition of hemosiderin that follows clinically appear as hyperpigmentation, which can occur in a reticular distribution. It has also been proposed that the distribution of affected blood vessels—predominantly in the superficial subcutaneous plexus (found in the papillary dermis)—results in the net-like pattern of erythema ab igne skin lesions.

Treatment Discontinuing contact with the heat source is the initial treatment of erythema ab igne. If the area is only mildly affected, with slight redness, the condition may resolve after a few months. If the condition is severe and the skin pigmented and atrophic, then it is unlikely to resolve. In this case, there is a possibility that a squamous cell carcinoma, or a neuroendocrine carcinoma, such as a Merkel cell carcinoma, may form. If there is a persistent sore that does not heal or a growing lump within the rash, a skin biopsy should be performed to rule out the possibility of skin cancer. If the erythema ab igne lesions demonstrate pre-cancerous changes, the use of 5-fluorouracil cream has been recommended. Abnormally pigmented skin may persist for years. Treatment with topical tretinoin or laser treatment may improve the appearance.

Epidemiology Erythema ab igne was once commonly seen in the elderly who stood or sat closely to open fires or electric heaters; however, erythema ab igne has been reported in both young and elderly individuals. Women have a higher incidence of erythema ab igne than men. Although wide use of central heating has reduced the overall incidence of erythema ab igne, it is still sometimes found in people exposed to heat from other sources, such as heating pads, space heaters, hot water bottles, and electronic devices.

See also Livedo reticularis Miliaria Vasculitis

References

Further reading Miller, Kristen; Hunt, Raegan; Chu, Julie; Meehan, Shane; Stein, Jennifer (October 2011). "Erythema ab igne". Dermatology Online Journal. 17 (10): 28. doi:10.5070/D347z4v01z. PMID 22031654. Ozturk, Murat; An, Isa (July 2020). "Clinical features and etiology of patients with erythema ab igne: A retrospective multicenter study". Journal of Cosmetic Dermatology. 19 (7): 1774–1779. doi:10.1111/jocd.13210. PMID 31696628. Abasszade, Joshua Haron; Abrahams, Timothy; Kuan, Chih Chien; Lau, Lik Hui (May 2023). "Erythema Ab igne". BMJ Case Reports. 16 (5) e255308. doi:10.1136/bcr-2023-255308. PMC 10173989. PMID 37160374. Harview, Christina L; Krenitsky, A (April 2023). "Erythema Ab Igne: A Clinical Review". Cutis. 111 (4): E33–E38. doi:10.12788/cutis.0771. PMID 37289686.

External links "Image Challenge: December 31, 2009". The New England Journal of Medicine. DermNet vascular/erythema-ab-igne

Illustrations

Erythema ab igne illustration
Erythema ab igne: Reticulated, interlacing, hyperpigmented patches with a few, scattered, erythematous macules at junctions on the medial aspects of the lower legs
Reticulated, interlacing, hyperpigmented patches with a few, scattered, erythematous macules at junctions on the medial aspects of the lower legs

Worked examples

Example 1 — a first encounter with Erythema ab igne

Start with the simplest possible case. Write down what Erythema ab igne claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Erythema ab igne before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Erythema ab igne ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Erythema ab igne

In research
Erythema ab igne appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Erythema ab igne in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Erythema ab igne is common in secondary-school and first-year university syllabi. It links to neighbouring topics Skin conditions resulting from physical factors, so understanding it makes those chapters shorter.
In everyday life
Look for Erythema ab igne outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Erythema ab igne in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Erythema ab igne means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Erythema ab igne out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Erythema ab igne in simple terms?

Erythema ab igne (Latin for 'redness from fire'), or EAI, also known as hot water bottle rash or toasted skin syndrome, is a skin condition caused by long-term exposure to heat (infrared radiation). Prolonged thermal radiation exposure of the skin can lead to the development of reticulated erythema…

Why does Erythema ab igne matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Erythema ab igne?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Erythema ab igne.

Tags

  • Skin conditions resulting from physical factors

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