Psoriasis and eczema (dermatitis) are both skin conditions that result in itchy rashes, and it can be difficult to tell them apart. Normally, you will have only one or the other of these conditions, and they are treated differently, so it is important to get a proper diagnosis from a dermatologist to keep the symptoms and complications under control.
Identification
Most people with psoriasis have "plaque psoriasis" which is a build-up of dead skin cells that cause raised patches with white or silver scales. Eczema manifests as dry, red, scaly or blister-like skin that often itches before a rash appears.
Location
Psoriasis affects the scalp, knees, lower back, elbows, fingernails and toenails. Eczema often affects the hands and feet and is also common in the bends of the elbow and behind the knees.
Causes
The causes of psoriasis and eczema are not clear, but it appears that different immune system pathways play a role in the development of each condition. Genetic make-up may encourage psoriasis. Eczema appears to be related to allergies.
Triggers
Skin injury, sunburn, dry air and medications such as beta-blockers and lithium trigger psoriasis. Irritants such as dust, soap, wool and even one's own sweat can trigger eczema. Stress and upper respiratory (viral) infections can also cause flare-ups in both conditions.
Treatment
Psoriasis is treated with creams that contain salicylic acid, lactic acid, retinoids and coal tar and drugs known as biologics. Eczema is treated with corticosteroid creams, antihistamines and drugs known as calcineurin inhibitors.
