Wetness
In severe eczema, or after a prolonged period of scratching, the skin’s protective character can be reduced further and the skin becomes wet with colourless fluid that has oozed from the tissues, sometimes mixed with blood leaking from damaged capillaries (small blood vessels). Wetness usually occurs when eczema is at its most itchy and is very likely to become infected. Some wetness may come from small vesicles (pin-head blisters), which burst when scratched. These are most commonly found on the hands and feet, along the edges of the digits or on the palms or soles.

Structure of the skin
The skin is your largest organ, weighing about four kilograms and covering about two square metres. It is your interface with the environment, protecting you against chemicals, bacteria and radiation, helping you to maintain a stable body temperature, and stopping you from losing fluid and vital body chemicals. Your skin contains nerve endings that allow you to feel touch, temperature and pain. Nails, which are also part of your skin layer, are useful for prising things open, among other things. Skin is strong and resilient, yet also flexible.

The skin is made of three layers: epidermis, dermis and fat.

Epidermis
The outer layer is the epidermis, which contains sheets of epithelial cells called keratinocytes. These keratinocytes are produced at the junction between the epidermis and the second layer of skin, the dermis. The epidermis is supported from below by the dermis.

The epidermis contains many layers of closely packed cells. The cells nearest the skin’s surface are flat and filled with a tough substance called keratin. The epidermis contains no blood vessels – these are all in the dermis and deeper layers.

The epidermis is thick in some parts (one millimetre on the palms and soles) and thin in others (just 0.1 millimetre over the eyelids). Dead cells are shed from the surface of the epidermis as very fine scale, and are replaced by other cells which pass from the deepest (basal) layers to the surface layers over a period of about four weeks.

The dead cells on the surface take the form of flattened, overlapping plates, closely packed together. This layer is known as the stratum corneum and is remarkably flexible, more or less waterproof and has a dry surface so that it is inhospitable to micro-organisms.

Dermis
The dermis is made up of connective tissue, which contains a mixture of cells that give strength and elasticity to the skin. This layer also contains blood vessels, hair follicles and roots, nerve endings, and sweat and lymph vessels and glands. The elements of the dermis all carry messages or fluids to and from the epidermis so it can grow, respond to the outside world and react to what goes on inside the body.

Fat
Underneath the dermis is a layer of fat which acts as an important source of energy and water for the dermis. It also provides protection against physical injury and the cold.