I want to know more about what is eczema.

Eczema is a form of dermatitis, or inflammation of the upper layers of the skin.
The term "eczema" is broadly applied to a range of persistent skin dryness or recurring skin rashes characterized by redness, skin edema, itching and dryness, with possible crusting, flaking, blistering, cracking, oozing, or bleeding. Areas of temporary skin discoloration sometimes characterize healed lesions, though scarring is rare.

Eczema

圖片參考：http://upload.wikimedia.org/wikipedia/en/thumb/f/ff/Dermatitis.jpg/190px-Dermatitis.jpg

Typical,mild dermatitis

Eczema is also a general term encompassing various inflamed skin conditions. It is most often characterized by dry, red, extremely itchy patches on the skin. Eczema is sometimes referred to as "the itch that rashes," since the itch, when scratched, results in the appearance of the rash.
Eczema can occur on just about any part of the body; however, in infants, eczema typically occurs on the forehead, cheeks, forearms, legs, scalp, and neck. In children and adults, eczema typically occurs on the face, neck, and the insides of the elbows, knees, and ankles. In some people, eczema may "bubble up" and ooze. In others, the condition may appear more scaly, dry, and red. Chronic scratching causes the skin to take on a leathery texture because the skin thickens (lichenification).

圖片參考：http://www.skincarephysicians.com/eczemanet/images/baby3.jpg

eczema的中文名稱應是皮膚敏感發炎

As far as I know, eczema usually happens due to inheritance from your older generation. People with asthma or 鼻敏感 tend to have it too. usually it's localised in certain skin areas and may happen more easily when the weather is dry.
THis is just out of the limited knowledge I have. Pls treat it as my personal comment only