Experts aren't sure what causes pityriasis rosea. Unlike many other skin conditions, it is not an
allergic reaction or caused by a
fungus or bacteria. And there aren't signs that it is caused by a virus. But something irritates the skin and causes the rash.
What are the symptoms?
Pityriasis rosea causes a
The rash often begins with a single, round or
oval, pink patch that is scaly with a raised border (herald patch). The size of
the patch ranges from
2 cm (0.8 in.) to
10 cm (3.9 in.). The larger
patches are more common. See a picture of a
Days to weeks later, salmon-colored,
1 cm (0.4 in.) to
2 cm (0.8 in.) oval patches
appear in batches on the abdomen, chest, back, arms, and legs. Patches
sometimes spread to the neck but rarely to the face.
Patches on the
back are often vertical and angled to form a "Christmas tree" or "fir tree"
The rash does not cause itching in 25% of people who have pityriasis rosea. For 50% of people, the itch is mild to moderate. And for 25% of people, the itch is severe.1
The rash usually lasts 6 to 8
weeks, but it can last up to several months.
The rash may take other forms. Rounded bumps (papular rash)
may be seen in young children, pregnant women, and people with dark skin.
Blisters (vesicular rash) may be seen in infants and young children. In some
people, the herald patch may not appear, or two herald patches may appear close
Before the herald patch appears, you may feel tired and
as though you have a cold. You may have a headache, nausea, sore throat, and
loss of appetite.
A rash similar to pityriasis
rosea also can be caused by
syphilis and by certain medicines such as
If you get a rash on the palms of your hands or the soles of your feet, see your doctor. This can be a sign of something more serious than pityriasis rosea.
How is pityriasis rosea diagnosed?
will diagnose pityriasis rosea by looking at the rash. Diagnosis can be
hard when only the herald patch is visible, because the condition is often
mistaken for ringworm or eczema at this time. After the rash appears, diagnosis
is generally clear.
If the diagnosis is unclear, your doctor may
potassium hydroxide (KOH) test to make sure the rash
is not caused by a
fungal infection. A skin sample may be taken from the
infected area and examined under the microscope (biopsy). If the
diagnosis is unclear in a sexually active person, a test for syphilis is often
How is it treated?
Pityriasis rosea goes away without treatment. It usually lasts about 6 to 8 weeks. If the rash itches, you may wish to use skin lotions and lubricants to soothe itching. If symptoms are severe, your doctor may prescribe anti-inflammatory medicines such as corticosteroids to relieve itching and reduce the rash.
Although treatment isn't needed, antiviral medicines like acyclovir may shorten the time you have the rash, especially if you take them when the rash first starts.
the rash to sunlight may make it go away more quickly. But exposing your skin
to the sun too long can result in sunburn and increase your risk of
If the rash lasts more than
3 months, contact your doctor.
To relieve itching at home:
Keep the itchy area cool and moist. Apply
washcloths soaked in ice water. But remember that repeated wetting and drying
will actually dry out your skin. Dry skin can make itching caused by a rash
Avoid taking hot showers or baths. Keep the water as cool as
you can tolerate.
Try an oatmeal bath, such as Aveeno Colloidal
Oatmeal bath, to help relieve itching. You may also wrap
1 cup of oatmeal in a cotton cloth and boil as
you would to cook oatmeal. Use this as a sponge and bathe in cool water without
over-the-counter 1% hydrocortisone cream for small
itchy areas. Use the cream very sparingly on the face or genitals.
Note: Do not use the cream on children younger than age
2 unless your doctor tells you to. Do not use in the rectal or vaginal area in
children younger than age 12 unless your doctor tells you to.
antihistamine, such as chlorpheniramine maleate
(Chlor-Trimeton) or diphenhydramine (Benadryl). Don't give antihistamines to
your child unless you've checked with the doctor first.
Apply a moisturizer or calamine
lotion to the skin while it is damp.
Wear cotton or silk clothing.
Avoid wearing wool and acrylic fabrics next to your skin.
little soap as possible. Use gentle soaps, such as Basis, Cetaphil, or Dove. Avoid deodorant soaps when you have a rash.
How this information was developed to help you make better health decisions.