The small red bumps experienced in this type of dermatitis are usually about 1 cm in size, red in color and may be found symmetrically grouped or distributed on the upper or lower back, buttocks, elbows, knees, neck, shoulders and scalp. The symptoms of seborrhoeic dermatitis, on the other hand, tend to appear gradually, from dry or greasy scaling of the scalp (dandruff) to scaling of facial areas, sometimes with itching, but without hair loss. In newborns, the condition causes a thick and yellowish scalp rash, often accompanied by a diaper rash. In severe cases, symptoms may appear along the hairline, behind the ears, on the eyebrows, on the bridge of the nose, around the nose, on the chest, and on the upper back. Complications
People with eczema should not receive the smallpox vaccination due to risk of developing eczema vaccinatum, a potentially severe and sometimes fatal complication. Other major health risks for people with dermatitis are viral and bacterial infections because atopic dermatitis patients have deficiencies in their proteins and lipids that have barrier functions along with defects in dendritic cells and as a result are unable to keep foreign invaders out leading to recurring infections. If left untreated, these infections may be life-threatening, so skin barrier improvement (such as daily moisturizing to minimize transepidermal water loss) and anti-inflammatory therapy are recommended as preventative measures. Cause
The cause of dermatitis is unknown but is presumed to be a combination of genetic and environmental factors.
Allergic contact dermatitis affects about 7% of people at some point in their lives. Irritant contact dermatitis is common, especially among people with certain occupations; exact rates are unclear. Types
Dermatitis includes:
Atopic dermatitis
Allergic contact dermatitis
Irritant contact dermatitis
Seborrhoeic dermatitis
Stasis dermatitis

Signs and symptoms
Dermatitis symptoms vary with all different forms of the condition. Although every type of dermatitis has different symptoms, there are certain signs that are common for all of them, including redness of the skin, swelling, itching and skin lesions with sometimes oozing and scarring. Also, the area of the skin on which the symptoms appear tends to be different with every type of dermatitis, whether on the neck, wrist, forearm, thigh or ankle. Although the location may vary, the primary symptom of this condition is itchy skin. More rarely, it may appear on the genital area, such as the vulva or scrotum. Symptoms of this type of dermatitis may be very intense and may come and go. Irritant contact dermatitis is usually more painful than itchy. Although the symptoms of atopic dermatitis vary from person to person, the most common symptoms are dry, itchy, red skin. Typical affected skin areas include the folds of the arms, the back of the knees, wrists, face and hands. Perioral dermatitis refers to a red bumpy rash around the mouth.Dermatitis herpetiformis symptoms include itching, stinging and a burning sensation. Papules and vesicles are commonly present.