Pityriasis rosea is a common, relatively short-lived skin disorder exhibiting a scary rash of symmetrical pink patches. The underlying cause is unknown, but an unidentified virus is believed to be the culprit. Even so, it is not contagious.
Pityriasis typically occurs during the spring and autumn months and affects mostly adolescents or young adults. It begins with a large pink spot -- called a herald or mother patch -- on the chest or back. (This initial patch is often mistaken for ringworm or an insect bite.) Within a week or two, other, smaller pink spots appear over the trunk, upper arms, and legs. The spots may also occur on the neck, but they rarely spread to the face. The rash on the trunk sometimes resembles an evergreen tree with drooping branches. On individuals who are suntanned, the rash may be confined to unexposed areas of the body, such as the breasts, armpits, buttocks, and pubic area.
Racial differences among pityriasis patients have been noted. In African-Americans, for example, the rash often covers the lower arms and legs in addition to the usual distribution, and the pink spots may give way to dark, hyperpigmented spots that persist for months after the rash disappears.
In about 50 percent of cases, the rash causes itching, which can be quite intense, especially if the person becomes overheated. In some instances, there is a more severe inflammatory skin reaction, often accompanied by other symptoms such as fatigue and achiness.
The rash usually fades and disappears within six weeks after reaching it's peak, but there have been cases in which it lasted much longer. Sometimes the patches show up in two or more waves, with subsequent waves appearing at intervals of up to several weeks after the first one. Occasionally, additional outbreaks occur after many months, and certain environmental or physical factors, such as overheating or developing some other type of skin irritation, can cause a worsening or even reappearance of the rash.
Diagnostic Studies and Procedures
A dermatologist usually can diagnose the condition by examining the skin for the characteristic herald patch. She will also check the appearance of individual lesions -- the lesions of pityriasis rosea typically have raised borders where scaling is most prominent -- and closely examine the distribution of the rash. If it has an unusual appearance, skin scrapings may be sent to a laboratory for analysis to rule out a fungal infection. Blood tests also may be ordered.
Pityriasis rosea is a self-limiting condition and will eventually clear up without treatment. If the itchiness interferes with sleep or other activities, steroids may be prescribed. Medicated lotions and lubricants may also be given to help alleviate itching. In severe cases, ultraviolet light treatments may help. Such treatments should always be supervised by an experienced health professional.
Herbal Medicine. Compresses soaked in witch hazel or an infusion of geranium, chamomile, lavender, or juniper berry are recommended to help ease the itching and skin inflammation. Ointments or salves that contain arnica, calendula, duckweed, or elder have been found effective too. A cucumber poultice is yet another method for relieving itchiness.
Hydrotherapy. A time-honored way to alleviate itchiness is to add two cups of apple cider vinegar to tepid bathwater. Alternatively, a cup of baking soda or a pint of thyme tea may help. Avoid hot baths and saunas, as heat often worsens the itchiness of pityriasis.
Hypnotherapy and Visualization. These techniques may be helpful in coping with itching. For example, by using self-hypnosis, an individual may be able to create a sensation of numbness in the itchy spots.
Resist the urge to scratch, which actually worsens the condition by setting in motion an itch-scratch-itch cycle. Scratching also can lead to infection. Nonprescription products such as hydrocortisone creams and calamine lotion applied to the rashy areas will usually ease the itching. Bath preparations containing colloidal oatmeal may also be soothing, but be sure the water is tepid rather than hot or cold.
Over-the-counter antihistamines such as Benadryl may also relieve itching, but they often cause drowsiness, which' may make it difficult to use these medications for long periods.
Because physical exertion and over-heating sometimes worsen the disorder, try to avoid vigorous exercise that is likely to produce sweating. And don't use strong soaps and cosmetics, as they may increase the irritation.
Exposing the rash to sunlight may hasten healing, but should be limited to a few minutes in the morning or late afternoon when you are less likely to become sunburned.
Other Causes of Itchy Rashes
Eczema and dermatitis cause itchy rashes, but unlike pityriasis, these conditions tend to be chronic. Psoriasis is also characterized by scaly lesions, but they are usually larger and thicker. Among infectious disorders, ringworm and other forms of tinea can produce an itchy, scaly rash that may be confused with pityriasis rosea, as may a reaction to penicillin and other medications.
Syphilis causes a red, scaly, bumpy rash during its second stage, usually about six weeks after the infection is contracted. Thus, a laboratory test to check out the possibility of syphilis is in order if such a rash is accompanied by a lever or enlarged lymph nodes in the neck, armpit, or groin.