Dermatitis is a medical condition that is characterized by an inflammation of the skin. The term is often used to describe itchy rash, blisters or bumps on the top layer of the skin on any part of the body. The most common types of dermatitis include contact, atopic and seborrheic.Contact DermatitisContact dermatitis is the skin's reaction, when it comes in contact directly with an irritant. The rash usually has well-defined contour and develops on the spot where the irritant touched the skin. It is usually accompanied by mild to severe itching that can last several days. Scratching may cause swelling and large blisters filled with fluid. Contact dermatitis does not spread if one touches the rash or the blister fluid. The rash can also be a result of a swallowed irritant or an allergen. Allergic reaction can appear on any part of the body, but is most common on the face, arms and the upper body.Atopic DermatitisAtopic dermatitis is a chronic skin condition that is common in people who have hay fever or Asthma. Itchy rash with oozing blisters can develop on large areas of the body, such as scalp, face, hands, elbows and behind the knees. Scratching leads to more inflammation and may cause infection if the skin is broken. The color of the patches may vary from light pink to deep red. These areas may be warm to touch.Seborrheic DermatitisSeborrheic dermatitis--most commonly known as dandruff--develops on the scalp and occasionally on other areas of the body. It is characterized by greasy scaling and flaking of the scalp that may get worse during the colder time of the year. It is usually not accompanied by hair loss. Seborrheic dermatitis causes severe itching. Infants usually get seborrheic dermatitis within the first three months after birth. It is also known as cradle cap and looks like large yellow flakes on the scalp. It may also be accompanied by red pimples on the face.While dermatitis itself is not a fatal disease, an excessive scratching can lead to bacterial infections. Also, if the dermatitis is a reaction to an allergen, it may be accompanied by an anaphylactic shock that can be fatal.