Introduction

Dermatitis is not a single disease -- rather the name covers those skin conditions in which inflammation is the key feature. As a result of inflammation, symptoms such as itching are common. Dermatitis is also called eczema, from the Greek ekzein, which means "to boil over or break out", because of the small blisters ('vesicles') that occur.

The chief signs of dermatitis are: redness ('erythema'), a rash (dry flaky skin with small blisters), and pain or itch.

Therefore, if you have areas of redness on the skin that are itchy and present with a rash, you are most likely suffering from dermatitis. The next step is to define the type of dermatitis. The three main types are atopic, allergic, and irritant contact dermatitis; these are discussed in more detail in subsequent articles.

What are the appearances of dermatitis?

As with many other inflammatory conditions (which often end in '-itis'), dermatitis may be acute, or chronic, or sometimes subacute. Commonly there are acute episodes ('flares') followed by quieter phases ('remissions'). If someone has had dermatitis for some time, i.e. chronic dermatitis, more permanent changes in the skin can occur.

In an acute episode there is mainly redness due to increased blood supply to the affected area. The blood vessels leak fluids and cells that collect in small blisters (vesicles) or sometimes large blisters ('bullae'). This is the typical rash of eczema.

Itch is the dominant symptom, and it can be intensely uncomfortable. It may begin before any changes in the skin are visible. Itch and the scratching that results are typically more intense in the evening, and may keep the sufferer (and his or her family) awake at night. They can produce lack of concentration at school or work, and can be an embarrassment in public places. In patients with atopic dermatitis scratching tends to occur more easily when the skin comes into contact with some irritants such as wool, acrylic, soaps and detergents or simply when the weather temperature are too high or too low.

As the person scratches their rash, the blisters are broken, and weep. When the fluid oozing out dries, it forms a crust.

Infection can occur if bacteria, such as a Staphylococcus, get into the broken blisters. In this case, 'white heads' filled with pus, ('pustules') can be seen on the skin surface.

Viruses can also invade affected areas, the best known being herpes.

During remissions, symptoms are less apparent or may be absent. However, a careful observer can detect presence of redness and scaling over the previously affected area. Redness and scaling are the main signs of subacute dermatitis. When the condition has persisted for some time (with several flare-ups and remissions) the inflammation, itch and their effects - mainly scratching - result in abrasions, thickening ('lichenification') and, in extreme cases, cracks ('fissures').

In lichenification, the normal surface pattern of the skin is exaggerated, with a criss-cross pattern of lines enclosing flat-topped, smooth, shiny patches, giving a tree-bark appearance.

Subsequent articles in this series will deal with the various types of dermatitis, their causes, who gets them, and how they can be treated. A very comprehensive dermatology online atlas includes hundreds of images of dermatitis that describe the multiple faces and given names of atopic dermatitis in the acute, sub-acute and chronic stages -- see the links below.