I have a birthmark where my buttcrack is extra long. the extra part is always red and inflamed and a foul smelling gunk builds up even if i clean.

Doctor can examine: Some people are born with a pilonidal cyst at the top of the butt crack. Sometimes the cyst gets infected and needs treatment, such as drainage or antibiotics. A skilled surgeon can remove the cyst after treatment. If not removed, the problem tends to recur. One can see her primary care doctor to get a diagnosis as to what her problem truly is, and then start whatever treatment process is needed.