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.

While it is possible that a virus causes pityriasis rosea, this skin disease does not seem to be contagious. It does not seem to spread from one person to another.

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.