Summer Penile Syndrome

Chiggers (tiny mites) and plants like poison ivy cause summer penile syndrome. Males are most at risk for developing this allergic reaction, which causes a swollen penis and an itchy rash around the genitals. Symptoms often improve with minimal treatment. You can take steps to lower your family’s exposure to chiggers and poison ivy.


What is summer penile syndrome?

Summer penile syndrome is a skin condition that mostly affects boys and children assigned male at birth (AMAB) during warm weather months. It can also affect adults. Exposure to chiggers or other mites or, very rarely, a plant like poison ivy causes an allergic reaction around the genitals. You or your child may experience itchy skin, red bumps and a swollen penis.

What’s the difference between summer penile syndrome and a rash?

A skin rash from chiggers or poisonous plants can affect people of all ages and genders. The rash may appear anywhere on your body. Summer penile syndrome occurs when the rash affects the penis, scrotum or other parts of the male reproductive system.

What are other names for summer penile syndrome?

You may also hear these terms:

  • Lion’s mane penis.
  • Seasonal acute hypersensitivity reaction of the penis.
  • Trombiculosis or trombiculiasis of the penis.

What are chiggers?

Chiggers belong to the Trombiculid family of mites. Mites aren’t insects. They’re in the same eight-legged arachnid family as ticks and spiders. Most chiggers are too small to see without a magnifying glass.

Chiggers prefer woods, grassy fields and moist areas where they can feed on plants and vegetation. Chiggers can be found in a lot of outdoor spaces, especially in the warmer, humid southern United States. They’re most active in the summer and early fall when temperatures are warmer. They die when temperatures drop into the 40s and below.


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Symptoms and Causes

What causes summer penile syndrome?

The baby form of chiggers (larvae) cause summer penile syndrome. The larvae attach to your clothes when you walk through an outdoor infested area. The tiny mites then work their way to an exposed area of your skin. Chiggers also attach to pet fur, which means you can pick up the mites from touching an animal that has them.

Chigger larvae don’t actually bite. And they don’t burrow into your skin. Instead, they use their tiny (but sharp) claws to dig a small hole into your skin where they inject their saliva (spit). Enzymes in the saliva break down skin cells, which the larvae feed on to help them grow into adult chiggers. The chigger larvae fall off within 48 hours (or sooner if you scratch and dislodge them). But the skin around their spit-filled holes hardens, causing bumps to form. Within 24 to 48 hours, these bumps start to itch. The itching is an allergic reaction to the enzymes in the mites’ saliva.

Less commonly, a person develops summer penile syndrome from exposure to poison ivy, poison oak or poison sumac. An oily sap on these poisonous plants called urushiol causes a type of allergic contact dermatitis. Summer penile syndrome may develop if your genitals come in direct contact with the plants or if you get this oil on your hands and then touch your genitals.

What are the symptoms of summer penile syndrome?

Symptoms of summer penile syndrome include:


Diagnosis and Tests

How is summer penile syndrome diagnosed?

There isn’t a diagnostic test for summer penile syndrome. A healthcare provider will evaluate the symptoms and perform a physical examination. They may ask about recent activities that could’ve exposed you to chiggers or poisonous plants. Your provider may check for small nodules (bumps) that look like bug bites in the genital area. Rarely, a mite may still be visible on or near the affected skin.

Management and Treatment

How is summer penile syndrome treated?

Over-the-counter (OTC) oral antihistamines can ease an allergic reaction. You can also apply a cool compress to the itchy rash. Your provider may suggest a topical (skin) hydrocortisone cream. Severe symptoms may require oral corticosteroids.


How long does summer penile syndrome last?

Penile swelling typically improves in a few days. But it can take up to two weeks for the itching to subside.

What are the complications of summer penile syndrome?

Rarely, a person develops a bacterial skin infection like impetigo or cellulitis from a bug bite. Bacteria can enter the skin where the mites have caused breakdown or damage. Scratching the itchy rash can also damage the skin further, allowing infection-causing bacteria to enter.


Can you prevent summer penile syndrome?

These steps can protect you or your child from chigger bites and poisonous plants:

  • Apply an EPA-approved insect repellant that contains DEET.
  • Wear long sleeves and pants in grassy or wooded areas.
  • Tuck your pants into your socks or boots to minimize skin exposure.
  • Treat clothing and shoes with permethrin, an insecticide that works on mites.
  • Bathe or shower with warm soapy water as soon as you come indoors.
  • Wash outdoor clothes in hot water.
  • When camping, avoid using plants or leaves as a substitute for paper products, like toilet paper.

Outlook / Prognosis

What is the outlook for people with summer penile syndrome?

Summer penile syndrome is uncomfortable. And the appearance of a swollen penis can be alarming. Fortunately, the condition often improves with minor treatment. It rarely causes long-term problems.

Living With

When should I call the doctor?

Call your healthcare provider if you or your child has:

  • Swollen penis.
  • Pain when urinating or difficulty urinating.
  • Signs of infection like red streaks on the skin, yellow discharge or swollen lymph nodes.

What should I ask my provider?

You may want to ask your healthcare provider:

  • What caused the summer penile syndrome?
  • What is the best treatment for summer penile syndrome?
  • How can I prevent summer penile syndrome in the future?
  • Are there any complications I need to know about?

A note from Cleveland Clinic

An itchy rash near your child’s penis (or your own) along with swelling is certainly a reason to see your healthcare provider. Fortunately, summer penile syndrome is mostly an annoyance. Over-the-counter medications can provide relief until the symptoms go away in a week or two. If you live in an area where chiggers or poisonous plants are abundant, you can take steps to limit exposure. For instance, wear long pants and long-sleeved shirts. You can also apply insect (mite) repellants.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 10/10/2022.

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