Hi. My Girlfriend Has A Quarter Sized Patch Of Alopecia

Hi. My girlfriend has a quarter sized patch of alopecia on her scalp about 2 inches up from the hairline. In the middle of that quarter sized area in what started out about 4-5 weeks ago ,is what appears to be a small bug bite. On examining it today, that small bug bite has increased in diameter. She says it itches and is sometimes sore. Can you please provide any possible explanations and if appropriate, any recourse of action. Thank you for your time