It is true that seborrheic dermatitis is more common in people with HIV, but that doesn't mean that the condition indicates enhanced risk of having HIV. Seborrheic derm is an exceedingly common condition, which includes everybody with dandruff! And your dermatologist is correct: the seb derm associated with HIV tends to be severe and difficult to control, pretty much exclusively in people with advanced immune deficiency, i.e. those with overt AIDS. Therefore, seborrheic dermatitis probably never is the only manifestation of HIV disease. If yours were due to HIV, you would be losing weight, having fever, and probably would have had one or more life-threatening infections by now.
Every new medical condition "pops up suddenly"; diagnosis of something new says nothing about the cause. That you had a new sexual partnership a few years ago is equally immaterial. That statement applies to most of the US population; there must be millions of people with seborrheic dermatitis plus occasional new sexual exposures.
Since you're worried, have an HIV test. This is not "code" to suggest I really believe there is a signficant chance you have it. I do not. Assuming no other risks or symptoms for HIV, you can be sure of a negative result.
Best wishes-- HHH, MD
Thank you so much for the quick reply. I do have dandruff and have had it since I was a teenager. I am starting to think that my main problem is from anxiey as I have been worried about HIV since I was young.
I guess I had misinformation about SD and HIV. I guess it would be crazy to think that SD would just show up a couple of weeks after a sexual encounter and be with me all this time with no other symptoms if it were truly being caused by HIV.
I do feel much better. Thank you.