A longstanding super itchy rash on arm

M has a super itchy rash on her arm for some years.  She scratches almost all the time.  Rarely, the rash appeared to have "vanished", only to return with a vengeance some days afterwards.  She tried moisturizing but it didn't improve.

You can clearly appreciate the presence of many criss-crossing deep lines running across a large island of brown.  There are also a few reddish bumps which seem to have been recently scratched.  This is the classical appearance of chronic eczema; a specific name given to this rash with such deep perpendicular lines is lichen simplex chronicus.  This is an extremely itchy form of localised eczema.  In fact, scratching it is almost always a pleasurable experience (i think some people deliberately scratch to temporarily relieve stressful moments)!  This type of eczema will not go away with just moisturizing; one needs to see a doctor for some powerful steroid ointment to bring it down!