Dark Patches On Penis, Spreading Condition, No Pain, No Increased Sensitivity. Causes ?
Thanks for posting your query
Dark circle like appearance on the penis can be due to inflammation and usually resolves by itself in few days time.Other than that it can be due to trauma,dry masturbation,age spots etc.
Since there is no pain,discharge,ulcer or any other symptom possibility of any infectious cause seems remote.
Sometimes age related spots can also arise on the penis due to abnormal pigmentation and insufficient exfoliation of the area with the advancing age. A possibility of that can be considered.
You can wait and watch and if there is development of any other symptom as pain,blister formation,fever,lymphadenopathy etc then a physical examination would be required.
Meanwhile follow general cleanliness measures as washing the area with antibacterial soap and water,keeping it dry and wearing clean undies.
Hope this information is adequate and answers your query. I will be available for follow up if any.