As a medical tern, “eczema” (fíom the Gíeek eczema: ”boil oveí, bíeak out”) is often used to describe any number of itchy, rash-like skin conditions, no matter their cause. In this way, it is something of a catch-all, encompassing an entire category of chronic symptoms. Eczema is also sometimes used to refer to specific types of the condition, such as the common atopic dermatitis.

In general, eczema is characterized by inflammation and irritation, typically developing as itchy and uncomfortable patches. The specific type of the condition is determined by a number of factors, including what triggered the reaction, where the reaction develops on the body, and how it appears.

If there is one type of eczema practically synonymous with the name, it’s atopic dermatitis. Characterized by periodic itchy rashes and dry skin, it impacts about one in 10 Americans, typically starting in childhood by about 5 years old. Some people “outgrow” the condition by the time they reach adulthood, while others suffer from symptoms for their entire lives.

Irritation and allergic reactions can result from the skin coming into contact with any of more than 15,000 different chemicals and substances, from wool to nickel, cosmetics to cleaning supplies. Poison ivy is the classic type of contact dermatitis. As with other types of the condition, itching and redness can be expected. Some people also develop small blisters.

Also known as pompholyx, dyshidrotic eczema causes tiny, often particularly itchy blisters to form in response to specific stimuli, whether excessive hand washing, certain chemicals, temperature fluctuations, or emotional stress. Flare-ups may be rare and isolated events or frequent and lifelong.

Itchy patches tend to be flat, but if the sensation is accompanied by round, raised spots, the problem may be nummular. This type gets its name from the Latin word for coin, which describes the general shape and size of the dry and itchy patches.

When blood is unable to move as it should through leg veins, the problem is known as veinous insufficiency. If this happens, the blood can pool in the lower extremities and build pressure in the capillaries, eventually “spilling” fluid into the skin itself. This leads to stasis dermatitis or gravitational dermatitis. Symptoms include swollen ankles, discoloration on the legs and feet, and the itching and dryness common to other types. Patients are typically older.

Chapped, cracked, and crusty skin on the hands may be hand eczema, especially if symptoms also include a burning sensation, blisters, discoloration, and scales. Harsh chemicals and allergens are common triggers, but even water can prompt a flare-up due to frequent hand- washing.

Patients with eczema may develop neurodermatitis, which can involve intense itching, skin thickening (also known as lichen simplex chronicus), and other symptoms.