recurring unexplained rash.. what should i get checked for

Ok I am going to see a doctor (again soon) and I would like advice on what I should get checked for.
Here are symptoms:

2 Years ago I had a huge case of athletes foot. Doc treated it with Griseofulvin (antifungal) It did a good job on the feet but then I got a different rash all over my body. Doc and I both though allergic reaction so he took me off those meds and started me on a corticosteroid. It did great.. but when I finished the cycle the rash came back, little slower than before but it came back.

Next I went to a dermatologist.. he gave me a longer cycle of corticosteroids. worked, but came back.  No matter what I do this rash just keeps coming back. No my 9 month old daughter has what looks like the same rash all over her back and chest. Now I'm worried for real.

Next week I'm going to the regular doctor and after that to a dermatologist. I would like advice on what I should get checked for.

Right now I'm thinking get checked for : Allergies, Syphilis, Kaposi Sarcoma
Anyone reccomend anything else?

[Sailor2007]

Oh Also the rash likes to migrate.. if I'm sweating a lot in a certain area it will pack up and move there. Like if I'm doing alot of physical stuff at work it will all move to near my underarms etc..

Anyone have any clue what this might be? I was scared it might be HIV or something but I was tested recently.