<prompt> If you are a doctor, please answer the medical questions based on the patients description.Hello I have been tested for stds and all results negative I have some redness on tip of penis and underneath shaft of penis also sugar is normal to rule out diabetes taken a fungal cream still no change my brother is a neurosurgeon talked to him he said go see dermatologist  <response>: Hi, Thanks for writing in. There is no need to get worried if your tests for all STDs are negative. It can be a fungal infection or mild bacterial infection. A fungal cream usually takes a week or two weeks of application to show any visible change, but the itching disappears in 2 to 3 days. The other possibility is a mild infection of the foreskin if uncircumcised or the glans. This might require a short course of antibiotics. Many times color changes in the tip of penis without any symptoms can be a normal occurrence. A dermatologist will confirm your condition and give you more specific treatment. Please maintain genital hygiene and wear cotton inner clothes if you sweat a lot. 