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Pityriasis rosea is a common rash usually seen in individuals between the ages of 10 to 35 years old. The rash typically lasts six to eight weeks, rarely extending 12 weeks or longer. Once a person has pityriasis rosea, it generally does not recur in their lifetime. Pityriasis rosea characteristically begins as an asymptomatic single, large pink patch called the "herald patch" or mother patch, measuring 2-10 centimeters. The herald patch is a dry, pink to red patch which appears on the back, chest, or neck and has a well-defined, scaly border. One to two weeks following the initial appearance of the herald patch, a person will then develop many smaller pink patches across their trunk, arms, and legs. The second stage of pityriasis rosea erupts with a large number of oval spots, ranging in diameter from 0.5 centimeter (size of a pencil eraser) to 1.5 centimeters (size of a peanut). The individual spots form a symmetrical "Christmas tree" pattern following lines of cleavage. This rash is usually limited to the trunk, arms, and legs, rarely occurring on the face and neck. Pityriasis rosea generally spares the face, hands, and feet.

Complications of Pityriasis Rosea

  • Pityriasis rosea can cause severe itching, especially if you become overheated.
  • The rash usually fades without leaving any permanent marks. But, if you have dark skin, long-lasting flat, brown spots may remain after the rash has healed.

Causes of Pityriasis Rosea

The exact cause of pityriasis rosea remains unknown. Most recently, pityriasis rosea has been associated most strongly with a virus from the human herpes family called human herpes virus type 6 (HHV6). Pityriasis rosea is not caused by or known to be associated with the common types of herpes virus that cause genital or oral herpes. While the mode of transmission (how it gets passed between people) of pityriasis rosea is also unknown, respiratory contact has been postulated. Pityriasis does not seem to be directly or immediately contagious to close contacts or medical providers exposed to the rash. Most people with a known exposure to pityriasis rosea do not seem to contract the rash. Pityriasis is not an allergic reaction, sign of an internal disease, or a bacterial or fungal infection. Currently, pityriasis rosea is thought to be most likely a viral-associated rash due to the possible concurrence with mild flu-like symptoms and the fact that people tend to gain potential immunity after one outbreak.

Signs & Symptoms of Pityriasis Rosea

Most people do not notice any symptoms with pityriasis rosea except for the appearance of the rash itself. Mild, intermittent itching is reported in about 50% of individuals affected, especially when people become overheated from exercise or hot showers. Itching seems to increase with stress. Sometimes pityriasis is accompanied by flu-like symptoms, such as sore throat, fatigue, nausea, aching, and decreased appetite. Most people are otherwise in very good health and don't feel any other symptoms.

Diagnosis of Pityriasis Rosea

Pityriasis rosea is usually diagnosed by the skin appearance, particularly the onset of the distinct, large herald patch and the symmetrical Christmas tree orientation of the following outbreaks. Also, the herald patch tends to have a unique, fine scale with a definite border. To rule out other types of skin disorders, a physician may scrape the skin and use a quick prep fungal test called potassium hydroxide or "KOH" to detect fungus infection that could mimic pityriasis. Also, blood tests including rapid plasma reagent (RPR) may be done to detect secondary syphilis, which also may mimic pityriasis. In some cases, a skin biopsy may be required to detect fungus and other types of rashes.

Treatments of Pityriasis Rosea

  • Most cases of pityriasis rosea require no treatment and resolve spontaneously. Treatment is not necessary if the rash is completely without any symptoms. Typically, pityriasis will usually clear on its own in six to eight weeks without medical intervention or therapy.
  • The most common symptom is itching, which can be treated with topical steroid creams (like hydrocortisone cream, clobetasol cream, etc.) and oral antihistamines (like diphenhydramine [Benadryl], loratidine [Claritin], etc.). These will not shorten the duration of the rash but will decrease the itching. Another treatment for itching is UVB light or sunlight. However, exposure to sunlight increases the risk of skin cancer. Generally, the best treatment is to avoid being overheated by reducing exercise and avoiding hot showers and baths.
  • There has been some evidence of reduced duration of pityriasis rosea with the off-label use of the antibiotic erythromycin or off-label use of antiviral medications such as acyclovir (Zovirax) or famciclovir (Famvir). However, neither of these medications has been proven to be uniformly effective in the treatment of pityriasis rosea and they are not usually necessary or required for treatment.

Prevention of Pityriasis Rosea

There is no definitive prevention for pityriasis rosea, as the cause is not yet fully known. As with most viral infections, helpful prevention tips may include good basic hygiene, hand washing, and avoidance of ill contacts and of aerosolized respiratory droplets from people coughing or sneezing.

When to seek Medical Advice

See your doctor if you develop any of the following signs:

  • A large scaly patch on your back, chest or abdomen.
  • A rash across your back, chest or abdomen.
  • A rash on your arms, legs or face.

Also contact your doctor if you've been diagnosed with pityriasis rosea, and the rash doesn't go away within three months.

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