Hello,
Thanks for posting your query at DoctorSpring.com
I can understand your concern.
This seems to be secondary to shaving as you rightly mentioned. It doesn't seem to be a drug reaction. If it were a drug reaction it wouldn't just involve a localized area but would have been more widespread. Involvement of a mucous membrane i.e of the mouth, nose, eyes, genitals or anal area is common. Presence of hives like rash or fluid filled blisters could be present.
I would recommend application of cortisone cream mixed with Mupirocin cream twice a day for a week on the affected area. Also I would recommend you take a tab. Claritin once daily for a week.
In case there is no improvement or there is an increase in the rash I would recommend that you meet your dermatologist.
Please let me know if you have any queries.
Take care