What causes sores on the penis?

If you’ve just noticed a bump, mark or sore on your penis it’s only natural to be worried. But try not to panic because a range of conditions can cause sores on your penis. Some are mild and some more serious but even the serious ones can be treated. But that doesn’t mean you should ignore it either. If you’ve found something you need to find out what it is. Just in case.

Here we’ll run through the different causes of sores, bumps, marks and blisters on your penis. We’ll also explain how these marks look with each condition and what you need to do about them.

Sexually transmitted infections

Some sexually transmitted infections (STIs) can cause sores or other marks to form on your penis. These STIs are most often passed through having unprotected sex, although on rare occasions some can be caught through sharing objects with people. This can even include recently used towels.

The STIs most likely to leave blemishes on your penis include:

Genital herpes

Genital herpes is a skin infection caused by a herpes simplex virus.

You’ve probably seen a cold sore before. Cold sores are caused by a herpes infection in the skin around the mouth. Genital herpes is caused by a similar infection. But rather than infecting the skin around the mouth, the virus infects the skin on and around your genitals and on and around your buttocks.

Genital herpes causes outbreaks of blisters on your skin that look like clusters of small, fluid-filled red bumps. The blisters break and leak fluid onto your skin to form open sores with a crust around them. Other symptoms of genital herpes include:

  • Tingling, itching or burning around the infected skin
  • Swollen glands in your groin
  • Pain when you pee
  • Flu-like symptoms – usually only the first time you have an outbreak.

If you think you have genital herpes you should go straight to a sexual health clinic to have yourself tested and get a diagnosis. There’s no cure for genital herpes.

Unfortunately, you’ll have outbreaks for life but the best way to treat these outbreaks is with a prescription antiviral medication like Valtrex or valaciclovir. These medications can help make your outbreaks less severe and shorten how long they last.

Read more about treating genital herpes.

Pubic lice

Pubic lice – also called crabs – are tiny insects that can infect your genital region. They live in and around your pubic hair and feed on your blood. Pubic lice bite into your skin to get at your blood, causing small bluish marks to form on the skin on and around your genitals. Other symptoms of a pubic lice infection include:

  • Itching on and around your genitals and anus that gets worse at night
  • Black powder-like spots in your underwear (crab poo)
  • Mild fever
  • Tiredness
  • Irritability

Although an infestation of blood-sucking insects around your junk sounds horrific, as far as STIs go pubic lice is relatively easy to deal with. You should head to your nearest pharmacy, talk to your doctor or visit a sexual health clinic to get a diagnosis. You can also treat the lice at home with a shampoo that kills them.


Like pubic lice, scabies is a skin infection caused by tiny insects. With scabies, the insects dig into your skin to feed on your skin cells and lay their eggs. Scabies causes a rash of small blisters where the insects burrow into your skin. The blisters are red with fluid-filled tips that can burst to form sores.

Scabies blisters can also form in lines where the insects have moved over your skin. The blisters are often surrounded by patches of red, scaly skin too. Other scabies symptoms include:

  • Intense itching that gets worse at night
  • Inflamed skin
  • Irritability

See your pharmacist first if you think you have scabies as they can recommend topical treatments you apply to your skin to kill the scabies lice. If this doesn’t clear your scabies up you should see your GP to get a prescription-strength treatment.


Syphilis is a serious bacterial infection you catch through unprotected sex. One of the first symptoms of syphilis is a painless, red, firm and circular sore on or around your genitals or anus. You can have just one sore or a small number of them.

Other symptoms of a syphilis infection include:

  • A rash that can spread to other areas of your body like your hands and the soles of your feet
  • Fever
  • Swollen glands
  • Headaches

Syphilis is serious. It can lead to blindness, paralysis and can even be fatal. The good news is that it can be treated with antibiotics. If you have any reason to think you have syphilis then head to your nearest sexual health clinic.

Other causes of sores on the penis

A mark on your penis isn’t always a sign you have an STI. The following also commonly cause blemishes to form on and around your genitals:


Eczema is a group of skin conditions caused by your skin having an allergic reaction to something you’ve eaten or something around you – like dust mites or pollen. It can affect skin anywhere on your body including the skin on and around your penis. Eczema causes patches of dry red skin and rashes of small red bumps. In more severe cases your skin can crack and bleed. Fluid-filled blisters can also form which can burst to create sores.

If you think you have eczema talk to your GP. They may recommend moisturisers and antihistamines as well as changes to your diet.


Psoriasis is an autoimmune disease caused by your immune system mistakenly attacking healthy parts of your body, specifically tissue in your skin. This results in patches of accumulated dead and live skin cells forming on your body called skin plaques.

Psoriasis skin plaques usually look like raised areas of red skin covered by white flaky scales. These can form on and around your penis. Psoriasis on your penis head can look different however – more like a patch of shiny red skin without the scales, almost like a bruise.

You can’t cure psoriasis and it’s a condition that stays with you for life. But if you think you have it talk to your GP about treatments and how to live with the condition.

Bruises and carpet burns

You can bruise your penis if you or someone else is too rough with it. Likewise, carpet or friction burns can happen if you or something else rubs up against your penis and causes friction. This could be a carpet (we’re not judging) but you’re more likely to get friction burns on your penis from vigorous sex or masturbation. 

A bruise on your penis will look like a bruise elsewhere on your body. Friction burns look like raised patches of red skin – they sometimes form open sores and are painful to touch.

In both cases bruises and friction burns will heal if left alone. If you’re in pain or they’re particularly severe you can see a pharmacist or your GP.

A blister, blemish or other mark on your penis might be a bruise, psoriasis or eczema but it could be a sign you have an STI. If you have a mark on your penis you’re worried about and think it may be an STI you should find your nearest sexual health clinic and get it checked out. It might not be an STI. But if it is you need to get it treated as soon as possible.