There exist a few types of dermatitis, and the treatment varies, depending on the cause.
In contact dermatitis is important to determine what caused the irritation, and to avoid that factor. Helping in relieving redness and itching can be creams containing hydrocortisone or wet dressings that provide moisture to the skin.
Neurodermatitis treatment has as purposes to stop scratching and to avoid further aggravating your skin. You will have to wear a dressing that's difficult to remove and leave it on for a week or longer. You can use sedatives and tranquilizers to help you stop scratching (but only the doctor will determine which drugs you can use); wet compresses can provide relief, and hydrocortisone lotions and creams may help soothe your skin.
Frequently shampoo use is needed in seborrheic dermatitis, and then you will have to carefully rinse your scalp. Tar, zinc pyrithione, salicylic acid or ketoconazole is the active ingredient of the commonly used shampoos.
In atopic dermatitis, applying hydrocortisone- containing lotions is needed to ease signs and symptoms. Wet dressings with mildly astringent properties may be prescribed if the skin cracks open. These wet dressings will contract your skin, reduce secretions and prevent infection. To help maintain normal skin texture and reduce flares of atopic dermatitis there can be used tacrolimus and pimecrolimus, which belong to a class of medications called immunomodulators. However, these drugs should be used only when other treatment fails.
In statis dermatitis, there accumulates fluid in the legs or ankles for extended periods, and the treatment consists in correcting this. Wearing elastic support hose or even having varicose vein surgery may be needed.
Also, to soften the thickened, yet fragile, skin and to control infection, there can be used wet dressings.
Perioral dermatitis has a treatment which consists in the oral antibiotic tetracycline. In the initial phase, in order to reduce signs and symptoms of perioral dermatitis, there can be prescribed a very mild corticosteroid cream.

To prevent contact dermatitis it is necessary to avoid coming into contact with substances like poison ivy or harsh soaps.
To prevent future bouts of dermatitis it is important to avoid dry skin. Try to have a bath less frequently, use mild soaps, brush your skin rapidly with the palms of your hands or gently pat your skin dry with a towel after bathing. It is also important to moisturize your skin.