Itching all over, could it be allergies?

Patient: For the past week I started itching all over my stomach, lower back, and thighs with no visible rash or otherwise. It is going away as quickly as it came and I am so confused what it is. Any ideas? I had a risky sexual encounter about a month ago and am wondering if it is a skin issue such as scabies or if it is something worse like an early symptom of HIV infection. I have had no other symptoms though and there is nothing visible on my body.

Symptoms: Itching