What is pityriasis rosea?

Pityriasis rosea is a self-limiting rash that can occur in both adults and children. Pityriasis rosea is more common in children and young adults. It is actually most common in people aged between 15 and 40 years. It affects around one in a thousand people.

Although its exact cause is unknown, it is thought that this condition is triggered by a virus. It is not associated to food, medicines or stress. Pityriasis is not usually contagious so does not spread to other people.

What are the symptoms of pityriasis rosea?

The majority of people with pityriasis rosea feel well. You may have a mild headache, a fever, some nausea or notice you are more tired than usual. Any symptoms that do occur usually start before the rash appears. Some people develop intense itching before the rash actually first appears.

Around one in ten people also have affected areas in their mouths - for example, blisters or ulcers.

What is the rash in pityriasis rosea?

A herald patch usually appears on the skin first. This is usually an oval- or round-shaped patch which can vary from 2 to 10 cms in diameter. This is usually pink/red in colour. It most commonly appears on your chest or upper back although it can sometimes appear on your abdomen, neck, back, thigh or upper arms. However, many cases do not to have (or do not notice) a herald patch.

Around 5-15 days later a more widespread rash gradually appears over about 10 days. This rash can spread over most of your body. However, it does not usually affect your face.

The rash usually consists of oval-shaped spots 1-3 cm in diameter which are pinky in colour. These spots are smaller than the herald patch. Often the spots seem to form lines in parallel with your skin creases.

This rash may be very itchy. The rash fades in time but this may take several weeks. It leaves no marks or scarring. Second attacks are very rare, but have been reported.

This description is the typical case which most people seem to have. Occasionally, the rash may just affect the arms and legs. Rarely, it can cause scaling or flaking of the skin, which can be troublesome.

Pictures of pityriasis rosea can be found here: www.dermis.net/dermisroot/en/32735/diagnose.htm

What is the treatment?

Pityriasis rosea is a self-limiting condition that will clear itself naturally. It usually lasts for 6-8 weeks but can last as long as 3-6 months.

Although this rash disappears without leaving a scar, some people find they have marks of discoloration on their skin for a few months.

There is no treatment that will clear the rash quicker than its natural course. The following may be beneficial:

• Avoiding fragranced soaps, hot water, wool and synthetic fabrics may help to reduce any skin irritation.
• If the rash is itchy, as much as possible try not to scratch. It is thought that scratching can make itch worse and an itch-scratch vicious cycle may develop with regular scratching. (That is, you itch more because you scratch, so you scratch more because you itch more ... and so on.)
• Calamine lotion may be soothing to the skin and reduce the itching.
• Antihistamine tablets may help to reduce the itching. These can be prescribed by your doctor or bought from a pharmacy.
• Your doctor may prescribe a steroid cream if your itching is more severe.
• If symptoms are severe you may be referred to a skin specialist who may advise some ultraviolet light treatment.

References

• Allen RA; Pityriasis Rosea, eMedicine, Feb 2009
• Lim SH, Kim SM, Oh BH, et al; Low-dose Ultraviolet A1 Phototherapy for Treating Pityriasis Rosea. Ann Dermatol. 2009 Aug;21(3):230-6. Epub 2009 Aug 31. [abstract]