Extreme itching on scalp

Hello Doctor,

Description
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On 29 Jan 2007, I had an encounter with a East Asian female in US whose STD status is unknown. The complete encounter can be described as kissing, full body rubbing (without any genital) and the worst part was receiving unprotected oral sex for a very brief period (less than a minute 30-40 sec). After that it was self masturbation.
Since Feb 13-14 (which is approx 2 weeks later) I started getting this extreme itching on my scalp and also a little less extreme on my face and back of my ears.
On my face there is no visible rash. I tried to look on the scalp as much as possible. No visible sign of rash there also. Along with the itching the skin appears moderately dry even though I am drinking enough water. The itching temporarily goes away when I take shower but returns when the hair and face gets dry.
I visited my doctor. He did blood tests for allergy, but they were negative. Initially he gave me Hydroxyzine Hcl 25 mg tablets. That suppressed the itching, but once I was out of that dose, the itching returned. Then he gave me a dose of Methylprednisolone 4mg (21 tablets to be taken as 6, 5, 4 ...per day). That also suppressed the itching, but it came back after 4 days of completion of the dose.

I dont have any other issue till now.
Because of my encounter, I got my blood tested for HIV and Syphilis on 13Mar (6 weeks). They came out negative.

Question
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What could be the probable cause for this? I am a bit worried since no diagnosis has been made. I am planning to visit a dermatologist also, but want to take your opinion also.

Thanks

PS: I had submitted the same question at STD forum also, but the doctor said there that it is not related to STD, so I am less worried about STD now (thanks to him)

[Alan Rockoff, MD]

I think you probably have seborrheic dermatitis, and that the itch is related to that and to your fear that you picked up an STD.  Seborrhea does everything you describe.  It comes and goes for no special reason and is best treated with topical (external) cortisone, rather than internal steroids.  I'm confident that the dermatologist will confirm this diagnosis or one like it.  But nothing you describe sounds like an STD or anything related to your sexual encounter.

Best.

Dr. Rockoff

[mike999]

Thanks for the information. It is appreciated.
Is there any over the counter medicine/shampoo available which I can get from Longs/Walgreen or are they all prescription drugs?