context: You might have had rashes on your arms or legs, or even your face. But on your penis? It can happen, and many things can cause it. A rash can show up as red, itchy patches on the tip of your penis or on the shaft. It might appear as smooth, pink splotches, tiny bumps, or puffy welts. Rashes may be harmless or serious. They can come and go quickly, or linger. Balanitis is an inflammation of the head of the penis, also called the glans penis, or the foreskin. This inflammation is more common in uncircumcised males, which means that your foreskin is still intact. If you haven't been circumcised, it can be difficult to keep the skin beneath clean. Bacteria, sweat, and dead skin cells can build up and make the skin covering the head of the penis swell. This can lead to itching, rash, redness, and discharge under the foreskin. It can also hurt. Doctors call this balanitis. You have a higher chance of getting it if you have diabetes. That's because the sugar in your urine collects under your foreskin, where bacteria begin to breed. This red, itchy rash happens when an outside substance irritates your skin. Common culprits are chemicals in soap, cologne, detergent, or even spermicide. An outbreak usually develops within a few minutes to a couple of hours after contact. It's not contagious, but can linger for up to a month. If you develop a rash, think of any new products you might have used recently. Stop using them to see if your symptoms improve. Certain medications can trigger a rash. You might be allergic, or it could be a side effect of the medication. Anti-inflammatory medications, antibiotics, and pain relievers like Tylenol can cause what doctors call âfixed drug eruptions.â These affect the genitals and can cause swollen, red plaques with a gray center. They can also cause blisters and dark areas that appear once the inflammation goes away. The type of reaction you have, how soon it shows up, and how severe it is depend on the medication. This rash looks like deep red, shiny patches on the tip of your penis or on the shaft. Because it's an area you often keep covered, the rash stays moist. It doesn't develop thick scales like psoriasis does on other parts of your body. You can get it whether your penis has been circumcised or not. If you have sex with someone who has an infection or disease on their genitals, you can get it, too. Common STDs that might cause you to develop a rash on your penis include: Scabies . These tiny mites burrow under your skin and lay eggs, causing an acne-like rash and fierce itching. You get scabies by having skin-on-skin contact for an extended period of time with someone who has it. That's why a common way to get it is through sex. The itching can get worse at night. Scratching the area can lead to sores, which can become infected. Syphilis . Condyloma lata rash is linked to the secondary stage of this STD. It causes large, raised gray or white lesions on the genitals. You can get it if your penis has direct contact with a syphilis sore (called a chancre) during sex. Chancres don't itch, so you might not know you have one. Still, syphilis can lead to serious health problems. Genital herpes may cause ithcing, pain and sores in your genital area. If you have this diease, you may have no obvious signs or symptoms. You can be contagious even if you have no visible sores. There is no cure for genital herpes. But medications can help reduce the symptoms and the risk of spreading the infection to others. A painful rash and redness on the underside of your penis or the head of your penis can signal a yeast infection. Yeast is a common fungus, but when it grows too much, it can cause problems. A number of things can cause it to multiply, like humid conditions or if you have a weak immune system. Certain antibiotics can kill the bacteria that normally keep yeast growth in check, leading to a yeast infection. Even if you don't think it's something serious, a rash on your penis can affect your health in different ways. See your doctor right away if you have the following symptoms: The rash is painful It's on other parts of your body too, appears suddenly, or is spreading quickly (these are signs of an allergic reaction) The rash looks like blisters, or is turning into sores Your penis feels warm or swollen, or the rash crusts over The rash leaks green or yellow fluid A red streak appears on your penis Go to the emergency room if you have a rash on your penis and a fever. This could signal an allergic reaction or severe infection.