Pityriasis rosea

What is pityriasis rosea?

Pityriasis rosea is a self-limiting rash that can occur both in adults and in children. Pityriasis rosea is more common in children and young adults. It is most common in people aged between 10 and 35 years. It is more common in the spring and autumn months.

Its exact cause is unknown. No germ (bacterium, virus, or fungus) has been found in people with the rash. However, certain types of human herpes viruses may be a part of the cause. It is not associated with food, medicines or stress. However, some medicines can cause a rash which looks similar to pityriasis rosea.

Pityriasis is not usually contagious so does not spread to other people.

What are the symptoms of pityriasis rosea?

Most people with pityriasis rosea feel perfectly well but are aware of a rash. The rash may be itchy but is not always. Some people may have:

• A mild headache.

• A high temperature (fever).

• A feeling of sickness (nausea).

• A feeling of being more tired than usual.

Any symptoms that do occur usually start before the rash appears. Some people develop intense itching before the rash first appears.

Occasionally, some people also have affected areas in their mouths - for example, blisters or ulcers.

What does the rash look like 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 2-5 cms in diameter. This is usually pink/red in colour. It most commonly appears on your chest or upper back. It can sometimes appear on your tummy (abdomen), neck, back, thigh or upper arms. However, many cases do not have a herald patch or it goes unnoticed.

Around 5-15 days later a more widespread rash gradually appears over about 10 days. Most commonly this is on the back or the chest and abdomen. This rash can spread over much 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.

Pityriasis rosea on the abdomen

By Marekzerzan (Own work), CC BY-SA 4.0, via Wikimedia Commons

Further pictures of pityriasis rosea can be found at the DermNet NZ and DermIS websites - see references below.

Do I need any tests?

Usually no tests are needed. Your doctor will be able to diagnose pityriasis rosea from the typical rash. If the rash does not go away after three months, or if the itching is very bad, you may be referred to a skin specialist (dermatologist). You may also be referred if your doctor is not sure about the diagnosis.

What is the treatment for pityriasis rosea?

Pityriasis rosea is a condition that will clear itself naturally. No treatment is needed. It usually lasts for 2-12 weeks but can last as long as five months. Most commonly it lasts about five weeks before going away completely.

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

There is no treatment that will clear the rash more quickly than its natural course. The following may help if itching is a problem:

• Avoid fragranced soaps, hot water, wool and synthetic fabrics.

• 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.)

• Simple creams (also called emollients) may be soothing to the skin and reduce the itching.

• A menthol cream or ointment may be cooling and soothing.

• 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 very severe you may be referred to a skin specialist who may advise some ultraviolet light treatment. There is no definite evidence that this is effective; however, it is often tried. Other treatments, such as aciclovir, may also be considered.