Spongiotic dermatitis is a confusing phrase that actually means something quite simple. Dermatitis means inflammation of the skin and 'spongiotic' means that small blisters under the skin are part of the inflammatory picture. Another word for spongiotic dermatitis is 'eczema' although some doctors
use spongiotic dermatitis specifically to refer only to more severe cases of eczema.
Eczema is usually 'atopic' meaning that the skin inflammation that occurs is unusual and does not occur in people who do not have the disposition to it. This means that common substances and exposures, such as water, soap, foods, and cold weather cause itching, redness, scaling, and blistering spots on the skin.
Therefore, as you suggest, an important part of treating the condition is figuring out what triggers are bothering you and eliminating them. It is often helpful to avoid frequent showering and hot water, as these dry out the skin and make the itching worse. Similarly, you should use a good skin moisturizing lotion very frequently throughout the day.
After these steps, the next is to apply small amounts of a topical over the counter steroid cream, such as hydrocortisone. This will usually clear up the inflammation, however if not then you should see your primary care doctor
to have a stronger steroid cream prescribed.