One possibility that is coming to my mind is of poikiloderma of Civatte. It effects the side and front of neck and presents as red-brown with prominent hair follicles. It can be due to sun exposure and hormonal factors and treatment consists of sun protection, using non perfumed soaps and cosmetics, hydroquinone, use of alpha hydroxy-acids and tretinoin and pulsed dye laser (PDL) and intense pulsed light (IPL). My sincere advice is to get the diagnosis confirmed from a dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.