Eczema, or atopic dermatitis, and psoriasis are both fairly common, chronic skin conditions that can cause patients physical discomfort and embarrassment. The diseases originate from an immune malfunction and share some common symptoms and treatments, but there are important differences as well. Psoriasis actually alters the way skin cells are made, while eczema mainly increases their sensitivity to the environment.
Experts suspect that both eczema and psoriasis have their roots in a malfunction of the immune system. While the cause of the immune malfunction in eczema is not well understood, doctors have a good grasp of the underlying immune cell pathology that causes psoriasis. In psoriasis, white blood cells, called T cells, mistakenly attack the patient’s own skin, setting off a chain reaction that dilates blood vessels and attracts other white blood cells. The net result is increased production of skin cells that migrate too quickly to the surface, causing a pile-up of scaly-looking cells.
Psoriasis can occur anywhere on the body, including the scalp, fingernails and toenails. Although eczema can also occur anywhere, it tends to affect the bends of the elbows and knees, hands and feet, arms, ankles, face and chest, and the skin around the eyes. Classic lesions of psoriasis have a thick, silvery, scaly appearance on top of red patches. Affected nails become ridged and pitted. In addition, some people with psoriasis develop a specific form of arthritis. Patients with eczema often have, or ultimately develop, allergies or asthma. Patches of eczema tend to be red to brown, sometimes with small bumps that leak fluid. Though psoriasis can be itchy, eczema is almost always itchy and the sensation often peaks at night. Scratching the patches of eczema causes raw skin and crusted-over bumps.
Eczema most commonly affects infants and young children. The National Institute of Arthritis and Musculoskeletal and Skin Diseases notes that 85 percent of patients with eczema develop the condition before 5 years of age and that onset after the age of 30 is uncommon. In about half the patients, eczema will continue into adulthood. Eczema occurs more frequently in people who live in cities or in very dry climates. In contrast, psoriasis primarily affects adults and is less sensitive to environmental conditions.
Psoriasis triggers are generally physiological -- infections, skin injuries, some medications, smoking and drinking alcohol can all bring on or worsen an episode of psoriasis. Eczema triggers tend to be environmental factors like harsh soaps, itchy clothing, dust or sand, solvents and allergens.
Patients with both eczema and psoriasis might benefit from corticosteroids to reduce inflammation, or the use of phototherapy to stimulate healing. Antihistamines for eczema can help control inflammation and itching, but they are not useful for psoriasis. Treatments specific to psoriasis include calcipotriene, which is an artificial form of vitamin D, and topical retinoids, which are vitamin A derivatives that slow skin cell growth.