Eczema presents as patches of inflamed skin with indistinct, blurry edges that often weep or crust, typically in flexural areas like inner elbows and behind the knees, while psoriasis presents as well-defined plaques with sharp edges and silvery-white scale, typically on extensor surfaces like the outside of elbows and front of knees. The distinction matters because eczema is primarily a barrier dysfunction disease treated with emollients and trigger elimination, while psoriasis is an immune-driven condition of accelerated skin cell production that requires different treatment.
The visual difference
Eczema tends to present as patches of inflamed, weeping, or crusting skin with indistinct edges. The skin looks raw rather than defined. In lighter skin tones it appears red; in darker skin tones it can appear grey, purple, or ashen. It most commonly appears in the flexural areas: the inner elbows, behind the knees, the wrists, the neck, and around the eyes. The colour and border cues below shift with pigmentation, and eczema on brown and black skin sets out the papular, follicular and psoriasiform presentations that make the border and colour cues less reliable.
Psoriasis presents differently. The plaques are well-defined: you can usually draw a clear line around where affected skin ends and unaffected skin begins. The surface is covered in a silvery-white scale, which is the result of skin cells accumulating faster than they shed. Psoriasis most commonly appears on the extensor surfaces: the outside of the elbows, the front of the knees, the scalp, and the lower back.
If the edges are blurry and the skin is weeping, it's more likely eczema. If the edges are sharp and the surface is scaly, it's more likely psoriasis.
The itch difference
Both conditions itch, but the character is different. Eczema itch is intense and often described as maddening, the kind that compels scratching even during sleep. Psoriasis itch is generally milder and described more as a burning or stinging sensation. Scratching psoriasis can cause the Koebner phenomenon: new plaques appearing at the site of skin trauma.
The mechanism
Eczema is primarily a barrier dysfunction disease. The skin barrier is structurally compromised, often due to mutations in the gene that produces filaggrin, a protein essential to barrier integrity. This allows irritants and allergens to penetrate the skin, triggering an immune response.
Psoriasis is primarily an immune-driven disease. The immune system incorrectly signals skin cells to produce too rapidly: the normal skin cell cycle of 28–45 days accelerates to 3–5 days. The cells accumulate on the surface because they can't shed fast enough, forming the characteristic plaques.
Triggers
Eczema triggers are typically external: allergens, irritants, certain fabrics, soaps, hard water, pet dander, dust mites, certain foods, sweat, and cold or dry air.
Psoriasis triggers are more systemic: stress is a major trigger, as are infections, certain medications, alcohol, and smoking. External irritants play a smaller role.
Treatment
For eczema, the foundation of treatment is barrier repair: consistent use of emollients, avoiding identified triggers, and managing inflammation with topical steroids when needed. The xmahub protocol is built around this model.
For psoriasis, the treatment approach is different. Topical steroids are used but often combined with vitamin D analogues. More moderate to severe cases are frequently treated with systemic medications including biologics.
When you're not sure
If you genuinely cannot tell which condition you have, see a GP or dermatologist for a diagnosis before starting any treatment protocol. The visual differences are usually sufficient for a clinical diagnosis; a biopsy is rarely needed.