Hello. I had a ingrown hair infection almost 3-4 weeks ago. I witnessed pain and swelling on the right side of my jaw. I went to the ER, and was prescribed Sulfamethoxazole, and ibuprofen. I have taken both like prescribed, and soon the swelling went down. A week after taking it, a small circle area where the swelling was began to lose hair. that was a week ago, and now I have a small circle about the size of a penny where hair has yet to grow back on my chin area, near my jaw. What could be the possible reason for this?