What is eczema?

Eczema, also called atopic dermatitis, refers to skin conditions characterized by dry skin, rash, and persistent itch. It can affect people of all ages. Eczema has been called the itch that rashes, because the persistent itch leads to scratching, which causes the rash. Eczema is a terrible cycle of itch and scratch that is difficult to break.

Why so dry?
In patients with eczema, the skin loses its moisture rapidly, causing chronic dry skin. Lipids hold skin cells together. As discussed in Your Guide to Eczema by Sarah Wakelin, in some patients with eczema, not enough lipids are produced, leading skin cells to dry out and be lost more easily. This makes the barrier layer of the skin thinner and thus even more likely to dry out and crack. The cracks can let irritants into the skin, exacerbating the eczema.

Further, eczema patients do not produce enough of the oils made by the sebaceous glands. This also leads to very dry skin.

Why so rashy?
The dermis is the deeper layer of the skin. In the dermis are many blood vessels. White blood cells that fight infection come to the skin through these vessels. In patients with eczema, the natural barrier function of the skin has broken down. This allows irritants to enter the skin, which trigger more white blood cells being sent to the skin. These white blood cells trigger inflammation, releasing antibodies and cytokines to fight off bacteria or infections, even when they don't need to be fighting. Steroids are anti-inflammatory drugs to help limit this response.

Why so itchy?
When the white blood cells get to work in the cell, they can trigger nerve endings in the skin, causing the sensation of itch.