Pityriasis rosea is a skin rash caused by a virus. It tends to be common in autumn and spring, and young adults - particularly women - are most susceptible. It starts with a large scaled spot called a ‘herald patch’, which is then followed within a week by clusters of smaller patches. Often, the patches are confined to the upper body and may follow the ribs in lines. The rash lasts around one or two months then clears up completely.
There is no treatment available to speed recovery, but the symptoms can be managed. Generally, pityriasis rosea is a one-off event - once it has gone, the rash doesn’t reappear. No scars are left, although people with darker skin may have spots of skin discolouration for a little while. Pityriasis rosea isn’t thought to be highly contagious.
Symptoms of pityriasis rosea
The signs and symptoms of pityriasis rosea include:
- A large single spot (herald patch) forms.
- The herald patch is scaled and coloured red to tan.
- A fine rash of small spots starts to appear within a week of the first patch appearing.
- The spots become small oval patches that are coloured red to tan.
- The patches seem crinkly and loose in the centre.
- The rash may be itchy.
- The upper body and upper arms are usually affected.
- The patches may follow the ribs in lines.
- The rash may spread to the upper thighs.
- Occasionally, the rash may spread to include the neck and lower face.
Causes of pityriasis rosea
Pityriasis rosea is caused by a viral infection. The virus has recently been identified as one of the herpes viruses. Children and young adults are more susceptible, for reasons unknown. Recurrences are rare - a person who develops the skin rash has only a two per cent chance of experiencing it again. Pityriasis rosea doesn’t seem to be highly contagious, but other members of the household may prefer to practise more stringent personal hygiene just for peace of mind.
Diagnosis of pityriasis rosea
Pityriasis rosea can be mistaken for skin conditions such as tinea (a fungal skin infection also known as ringworm) or psoriasis, so careful diagnosis is needed. Other less common illnesses, such as syphilis, may also cause a similar rash. A skin biopsy of one of the patches may be taken for laboratory analysis.
Treatment for pityriasis rosea
It is not possible to make the rash disappear any faster, so treatment aims to manage the symptoms. Options may include:
- Avoid using soap as this can irritate the rash.
- Bathe using plain water or some kind of moisturiser, such as bath oil.
- Steroid creams can be used to help reduce itching.
- Oral antihistamines may help in cases of severe itching.
- Mild moisturising creams can be applied generously and often.
- Some cases may respond to ultraviolet light, so mild sunshine may be beneficial. However, avoid sunburn and don’t stay in the sun too long. Early morning or late afternoon are the best times.
- Phototherapy using UVB ultraviolet light may be helpful.
Where to get help
- Your doctor
- Australasian College of Dermatologists.
Things to remember
- Pityriasis rosea is a skin rash caused by a virus.
- It is characterised by the formation of a large scaled spot called a ‘herald patch’, which is then followed by clusters of smaller patches.
- The rash lasts around one or two months then clears up completely.
- There is no treatment available to speed recovery, but the symptoms can be managed in the meantime.
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