Erythema is formed by an increased supply of blood to the skin, leading to the dilation of normal dermal blood vessels and resulting in a visible reddening, especially on the face.
Here's a breakdown of the process:
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Increased Blood Flow: Erythema is primarily caused by an augmented flow of blood to the superficial layers of the skin.
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Dilation of Dermal Vessels: This increased blood flow causes the blood vessels in the dermis, the layer of skin beneath the epidermis, to widen or dilate.
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Reddening of Skin: The vasodilation brings more red blood cells closer to the skin's surface, making the skin appear red or flushed.
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Blanching: Erythema characteristically blanches, meaning it temporarily turns pale or white when pressure is applied. This is because the pressure forces the blood out of the dilated vessels. Upon release of the pressure, the redness returns as the vessels refill. Cooling the area will also cause blanching.
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No Clear Borders: The redness associated with erythema typically doesn't have sharp, well-defined borders, distinguishing it from other skin conditions.
Factors that can cause increased blood flow leading to Erythema:
- Inflammation: The body's response to injury or infection can trigger vasodilation.
- Infection: Certain infections trigger the body's inflammatory response, leading to erythema.
- Allergic reactions: Histamine release during allergic reactions can dilate blood vessels.
- Sun exposure: Ultraviolet (UV) radiation from the sun can cause inflammation and vasodilation.
- Exercise: Physical activity increases blood flow to the skin for cooling.
- Emotional responses: Blushing is a form of erythema caused by emotional factors.
- Certain medications: Some drugs can cause vasodilation as a side effect.
