The most common form (percentage needed) of Eczema is 'Atopic Eczema' - in this case 'atopic' meaning 'of unknown origin'.
It can occur anywhere on the body, but is common on the hands, elbows, knees, face and scalp.
A variety of factors, including environmental, diet, genetic, viral, and bacterial are known to be associated with the disorder. But no direct biological mechanism which explains the persistent skin outbreaks has yet been found.
Since the cause is unknown, current treatments are based around relieving the symptoms rather than 'curing' the condition.
More info: NHS England
Also see : Psoriasisplugin-autotooltip__plain plugin-autotooltip_bigPsoriasis
"Psoriasis is a long-lasting autoimmune disease characterized by patches of abnormal skin. These skin patches are typically red, dry, itchy, and scaly. On people with darker skin the patches may be purple in colour. Psoriasis varies in severity from small, localized patches to complete body coverage."