Strange design on chin

Nine years ago my son developed the strangest thing on his chin. He is now 27 years old. I guess I would have to call it a rash, but it looks nothing like any rash I've ever seen. It looks sort of like a large upside down E on his chin. The sides of the E are sort of rounded off. It starts under his bottom lip on both sidesof his mouth. It is sometimes bright red, and sometimes it is almost not there. It is about a quarter of an inch wide all the way along the E. It alway looks exactly the same, except that sometimes it is darker red than other times. When it gets bright red, it stays that way for weeks at a time. Sometimes it burns slightly, and sometimes itches slightly. The worst part is that it is really bad looking, and very embarrassing for him. It is not raised, nor are there ever any blisters, or draining. I think it sometimes looks like someone painted it on. Two years ago he went to a dermatologist, and it was diagnosed as Seborric Dermaitus, but after reading up on this, we think not. He also was told he may be allergic to something in his own skin. He was given Ketoconazole, and told to wash his chin in a tar extract shampoo. The doctor said not to worry, and it would go away. It has not gone away, and just recently looks worse than it ever has before. It may be sun sensitive,or heat sensitive. Sometimes it gets flaky. I don't know that this has anything to do with it, but I think I should mention it. Shortly before it broke out, nine years ago, he had been having oral sex with his girlfriend. It breaks my heart to see my son with this awful looking, red, upside down E on his chin. Thanks for any help and answers you can give us.

[Alan Rockoff, MD]

You got me.  I have never seen or heard of a rash shaped like an E.  I can say this: natural rashes are round or oval.  Skin changes which are geometric--lines, triangles, and the like--are often self-induced (from rubbing or scratching.)  

For diagnosis, he will need to see a doctor, and he certainly should.  But he has to be absolutely sure that he never rubs or picks at the area, so that the doctor can tell what it is.

Best.

Dr. Rockoff