Pityriasis rosea: This common skin disease causes patches on the skin. Your dermatologist may call the large patch a mother patch. The smaller patches are daughter patches.
Pityriasis rosea (pit-uh-rahy-uh-sis row-zee-ah) is a common skin disease that causes a rash. This rash usually disappears on its own without treatment. You can expect to see the rash for about 6 to 8 weeks. Sometimes the rash lasts much longer.
Some people who develop this rash see a dermatologist to get treatment for the itch.
When people get pityriasis rosea, they often have the following signs (what you can see) and symptoms (what you feel):
- Mother patch: The first sign of this rash is a single patch on the skin. Called a "herald" or "mother" patch, this patch is the only patch on the skin for about 2 weeks. This patch can get large. It feels scaly. People who have fair to olive-colored skin will see a pink or rose-colored patch. In people who have dark skin, the color varies from violet to dark gray.
- Daughter patches: Within a week or two, more patches appear on the skin. These patches are smaller and may appear on the chest, abdomen, back, arms, and legs. Sometimes these patches develop on the neck, face, and elsewhere on the skin. Patches can even develop inside the mouth. These patches are oval shaped. If many patches appear, these new patches may form a pattern on the back. The pattern often looks like a Christmas tree.
- Patch-free zones: Patches rarely appear on the face, scalp, palms, or soles.
- Itch: The skin can itch. About half (50%) of the people have itchy skin. The itch tends to worsen when the skin gets warm, such as when a person works out or takes a hot shower.Sometimes, a mother patch does not develop, just lots of daughter patches. Some people may get only a mother patch. It is rare for a person to get only daughter patches or a mother patch.
Who gets pityriasis rosea?
People of all ages and skin colors get pityriasis rosea, but this skin disease is more likely to occur:
- Between 10 and 35 years of age.
- During pregnancy.
What causes pityriasis rosea?
No one knows what causes pityriasis rosea. Research shows that it is not an allergy. We also know that fungi (plural of fungus) and bacteria do not cause this skin disease. A virus may be the cause, but researchers have yet to prove this.
It is possible that a virus causes pityriasis rosea, but this skin disease does not seem to be contagious. It does not seem to spread from one person to another.
How do dermatologists treat pityriasis rosea?
Pityriasis rosea usually goes away without treatment. You can expect to have the rash about 6 to 8 weeks before it disappears. Some people have it for 2 weeks. Occasionally, it lasts longer than 8 weeks.
If a patient has unbearable itching, a dermatologist may prescribe a medicine to help relieve the itch. Sometimes a dermatologist prescribes light treatments for the itch.