What is eczema?
Eczema or dermatitis is one of the most common skin complaints. Both words describe the same condition and can be used interchangeably - what one person calls eczema, another may quite acceptably call dermatitis. The word 'eczema' comes from the Greek word meaning 'boiling or bubbling through', while 'dermatitis' means 'inflammation of the skin'.
These names tell us that eczema is an inflammatory skin disease, and that with eczema there are extra red and white blood cells in the skin with a 'cocktail' of natural chemicals called 'antibodies' and 'cytokines'. A similar process happens naturally after an injury or bum, and the inflammatory reaction helps to fight infection and heal wounds. However, when this system is activated without an appropriate reason, as in eczema, the end result is an itchy, sore rash. Imagine that the white blood cells are soldiers trained to fight the enemy invaders (bacteria, viruses, etc.) and that they release chemicals called antibodies and cytokines as weapons. If the soldiers start to fight without an enemy they will end up causing unnecessary damage to their surroundings, in this case, the skin. This is a simplified way of thinking about eczema, but it helps to explain why anti-inflammatory treatment such as steroids can help this condition.
The inflammatory process in eczema affects both the epidermis and the underlying dermis. In the epidermis, the keratinocytes (skin cells) become bloated and swollen, making them pull apart from one another. The epidermis becomes like a water-logged sponge, which makes it feel swollen and raised, and the excess fluid can collect into tiny blisters. Chemicals called 'proteases' are activated, and these dissolve the 'glue' that holds the keratinocytes of the outer skin layers together. This makes them shed more easily, causing dryness and increased skin flaking. When the important vital outer layers are lost, the skin is no longer such an effective barrier and tiny surface cracks develop allowing moisture to escape and infections to enter. The increased blood flow in the dermis in eczema causes signs of redness (erythema) and swelling, and makes the skin feel hot. Inflammatory chemicals in the skin act on nerve endings to cause the uncomfortable, prickly itch (pruritus) and urge to scratch that is one of the most distressing symptoms of eczema.
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