Hello dr. i got a 4 generation hiv test at 23 days after my exposure date. i had a headache and was extremely tired before i took the test. the test came back non reactive. now i have a itchy rash from my ribs down to my knees. what could it be?

Your symptoms don't suggest HIV, and your test result proves HIV isn't the cause. It's impossible to have HIV symptoms with a negative AgAb (4th generation) blood test. But for conclusive proof you didn't catch HIV, have another test 6 weeks after your exposure. (There is no way to even guess at other causes of your symptoms. See a doctor if the continue or you remain concerned.)

I can't think of any STD that would cause such a generalized itchy rash. . Can you think of any triggers that could cause an allergic reaction? I recommend consulting a physician or a dermatologist for evaluation and advice. In the meantime an antihistamine can relieve your itching.