Scabies mites, known scientifically as Sarcoptes scabiei var hominis, are microscopic parasites that burrow into the top layer of a person’s skin. Here, they lay their eggs and cause intense itching.
The mites tend to prefer warm places, such as skin folds and the genital areas. On the penis and scrotum, they can lead to a crusted, blister-like rash developing.
In this article, we discuss what scabies is, the symptoms it causes on the penis, transmission, and risk factors. We also cover diagnosis, treatment, and prevention of scabies.
What is scabies?
Scabies is a skin infestation with tiny parasitic mites that are barely visible to the naked eye. The mites burrow into the top layer of a person’s skin where they lay their eggs.
The mites prefer warm locations, such as between folds of skin, and tend to infest body areas that include:
- the groin region
- the penis and scrotum
- the thighs and buttocks
- the waist area
- under the breasts
- the skin between fingers and toes
About 4 to 6 weeks after the initial infestation, people with scabies develop an immune reaction to the mites. This reaction causes a scaly rash that may itch, crust, or ooze.
Scratching the rash can lead to bacterial infections and impetigo.
Children, older people, and those with weakened immune systems are at particular risk of developing severe complications from impetigo. These complications can include cellulitis, skin abscesses, and sepsis.
Most people with scabies have only a dozen or so mites on their body. However, a severe form of scabies called crusted scabies, or Norwegian scabies, can infest a person with millions of mites.
Crusted scabies is more likely to occur in people with weakened immune systems, such as older individuals and those living with HIV.
Image credit: CDC/ Dr. Gavin Hart, 1975
Image credit: CDC/ M. Rein, M.D., University of Virginia; Susan Lindsley, 1975
Image credit: CDC/ Susan Lindsley, 1976
Image credit: CDC/ Dr. N.J. Fiumara; Dr. Gavin Hart, 1976
Image credit: CDC/ Stewart Brown, 1976
Image credit: CDC/ Susan Lindsley, 1976
Image credit: CDC/ Susan Lindsley, 1973
Image credit: Dogad75, 2015
Symptoms of scabies on the penis
When scabies mites infest a person’s penis, they can cause:
- intense itching that may worsen at night
- raised lines on the skin
- crusty, blister-like sores
In people who have not had scabies before, these symptoms can take up to 4 to 6 weeks to develop after they become infested.
Because skin-to-skin contact is how scabies spreads, the mites can move to other areas of the body that come into prolonged contact with the penis. A person may also notice symptoms on their thighs, hands, or buttocks.
Transmission and risk factors
Scabies is a contagious condition and can spread through direct skin-to-skin touching.
However, the mites cannot jump or fly, so people usually need to be in prolonged contact with each other. It is unlikely that a person will contract scabies from casual touching, such as handshakes, hugging, or brushing against someone.
Scabies mites commonly pass between adults during sex. Condoms do not prevent scabies.
It is also possible to become infested from sharing bedding, clothing, and towels with people who have scabies. Scabies is also more common in crowded or confined environments, such as nursing homes, prisons, and daytime centers.
A doctor can usually diagnose scabies with a physical exam. A person who has itchy skin with lines or marks that indicate burrowing probably has scabies. Blister-like sores on the wrists or between the fingers are also common since scabies can easily spread to the hands.
While most people experience itching in response to scabies, not everyone has these signs. However, a doctor can confirm a scabies diagnosis by taking a skin scraping and analyzing it under a microscope for the presence of mites or their eggs and fecal matter.
A doctor may prescribe scabicides to treat people with scabies.
Image credit: Arthur Goldstein, 2018
It is important to seek prompt treatment for scabies, especially for people with a weakened immune system. Delaying treatment increases the risk of developing secondary infections and passing the mites on to other people.
Doctors prescribe scabicides to treat people with scabies. Scabicides are medications that kill scabies mites and are available as lotions, creams, and pills.
When using these medications, it is important to follow the instructions from the doctor or pharmacist carefully. A person will usually need to apply a scabicide cream or lotion to the entire body from the neck down, not just on the affected areas. Itching may persist for several weeks after treatment has begun, even if all the mites are gone.
It is also essential to avoid sex until the mites have completely disappeared. Doctors will usually recommend treating any recent sexual partners or anyone with whom the person has had prolonged close contact.
To prevent reinfestation, people with scabies and their sexual partners must decontaminate any clothing, bedding, or towels they have used during the 3 days prior to treatment. The Centers for Disease Control and Prevention (CDC) recommend doing this by either:
- washing items in hot water and then placing in a hot dryer
- having items dry cleaned
- sealing items in a plastic bag for at least 72 hours
Scabies mites can only usually survive 2 to 3 days away from human skin.
If bacteria also infect the scabies rash, a doctor may prescribe antibiotics. People with crusted scabies may need to stay in the hospital, especially if the infestation is severe, or the person has a weakened immune system.
If symptoms of scabies persist for more than 2 to 4 weeks after starting treatment, a person should go back to their doctor.
People can get scabies through direct and prolonged contact with someone who has scabies. The infestation commonly spreads through sexual contact, but it is also possible to get scabies through sharing infested items, such as clothing, towels, and bedding.
To prevent scabies, it is essential to avoid close contact or sharing linen with people who have scabies until they have completed their treatment. Wearing a condom during sex does do not prevent the transmission of scabies.
It is also important to note that symptoms can take 4 to 6 weeks to develop after the initial infestation. Even if they do not yet have any symptoms, a person with scabies can still pass on the mites to other people.
Anyone with symptoms of scabies should see a doctor as soon as possible to reduce the risk of spreading the infestation.
Scabies is a contagious skin condition that results from infestation with tiny parasitic mites. The infestation typically spreads when people have close, prolonged contact with each other, such as during sex.
Scabies usually causes intense itching and a red, spotty rash in areas where the mites have burrowed into the skin. The mites tend to prefer warmer areas of the body and often infest the penis and scrotum in males.
Scabies is rarely serious, but constantly scratching the rash can sometimes lead to secondary infections. People with weakened immune systems are also at risk of developing a more severe form of scabies known as crusted scabies.
People with symptoms of scabies should see a doctor as soon as possible to reduce the risk of spreading the infestation. Doctors can prescribe scabicide medications that can effectively kill the mites and treat the condition.