Psoriasis and pityriasis rosea are both common conditions that can cause scaly patches on the skin. However, the causes and other symptoms of these conditions are different.

Psoriasis is a chronic lifelong autoimmune condition that has no cure, while pityriasis rosea is temporary and generally clears up within a few weeks.

The symptoms of psoriasis can also resemble those of other skin conditions, including fungal infections, acne, and eczema.

In this article, we look at how to identify psoriasis and pityriasis rosea. We also discuss the causes and treatment of each of these conditions.

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Pityriasis rosea commonly affects the chest and neck.

Psoriasis is an autoimmune disease that causes inflamed, dry, red, and scaly patches to develop on the skin. It is most likely to appear in people aged 15 to 25.

People with psoriasis tend to experience flare-ups with periods of remission between them. There is no cure for psoriasis, but there are ways to manage it.

There are several types of psoriasis, including:

  • Plaque psoriasis, which causes dry, raised, red plaques that can be itchy and painful.
  • Guttate psoriasis, which occurs as a result of bacterial infection and causes small, scaling lesions in the shape of water drops. It usually resolves without treatment once the infection has gone.
  • Inverse psoriasis, which affects the areas within folds of skin and may develop due to a fungal infection.
  • Pustular psoriasis, in which red skin surrounds white pustules or blisters, usually on the hands and feet. Despite its appearance, this form of psoriasis is not an infection and is not contagious.
  • Erythrodermic psoriasis, a severe form of psoriasis that produces a fiery redness over most of the body. Symptoms include severe itching and pain, and the skin often peels off in sheets. It is rare and generally occurs in people who have plaque psoriasis.

People may mistake plaque psoriasis or guttate psoriasis for pityriasis rosea.

Pityriasis rosea is another common skin disease that causes scaly patches of rash on the skin. It tends to present initially with a large patch of rash, which is called the herald or mother patch. Smaller patches called daughter patches then follow.

These rashes may appear on the chest, abdomen, back, arms, legs, or neck. They rarely affect the face, scalp, palms, or soles of the feet.

Pityriasis rosea is most common in people between the ages of 10 and 35, but it is also more likely to occur during pregnancy.

Neither psoriasis nor pityriasis rosea is contagious, so these conditions will not spread between people.

Psoriasis and pityriasis rosea both cause patches of scaly, red skin, but the patches form different patterns. The conditions also progress differently.

Symptoms that are specific to psoriasis include:

  • red, inflamed, raised patches of skin with a covering of thick, silvery scales
  • small areas of scaly skin
  • dry skin that may crack or bleeditching, burning, and pain around the patches
  • thick, pitted, and ridged fingernails or toenails
  • swollen and painful joints, if a person has psoriatic arthritis

The symptoms of pityriasis rosea include:

  • a mother patch, which is a large, scaly patch of skin that appears violet or dark gray on dark skin and pink on fair skin
  • multiple smaller daughter patches on the chest, abdomen, back, arms, and legs that appear 1 to 2 weeks after the mother patch
  • itchy skin, which may affect around 50 percent of people with this condition

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Stress may trigger psoriasis flare-ups.

Doctors do not know exactly what causes psoriasis, but they believe that it is an autoimmune condition that may have a genetic component.

They are also unsure why pityriasis rosea occurs. This condition is not an allergy, and it does not develop as a result of fungi or bacteria. It may be the result of a virus.

While specific triggers, such as infection, stress, and certain lifestyle factors, can prompt a psoriasis flare, there are no known triggers for pityriasis rosea.

Psoriasis may need short-term or long-term treatment, depending on the type and how severe the symptoms are.

Treatment options include:

  • topical corticosteroids for inflammation and itching
  • moisturizers for dry skin
  • coal tar products to remove scales and soften the skin
  • salicylic acid for scaling
  • light therapy

Systemic medications work throughout the body. A person can take them as injections or by mouth. They include methotrexate, cyclosporine, and some types of retinoid.

Depending on the type of psoriasis and the severity of symptoms, a doctor may prescribe a biologic medicine. This is a long-term treatment that may help reduce the risk of flares and the severity of symptoms. Examples include etanercept (Enbrel) and infliximab (Remicade).

Pityriasis rosea usually resolves without treatment within 6 to 8 weeks. If necessary, a doctor may prescribe an anti-itch cream for severe itching.

Pityriasis rosea is not a severe condition, and it often resolves without leaving a trace. However, people with signs of pityriasis rosea should still visit a doctor to rule out other conditions. If they are experiencing severe itching, they can also ask for a prescription cream to provide relief.

People who have symptoms of psoriasis should visit a doctor for diagnosis and treatment. Anyone who also has any signs of infections, such as pain, swelling, or fever, should seek immediate medical care.

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Ringworm may appear similar to psoriasis or pityriasis rosea.

People may sometimes mistake psoriasis and pityriasis rosea for other conditions, including:

Psoriasis and pityriasis rosea cause similar patches of scaly, red skin, but they are separate conditions with different causes.

Psoriasis is a chronic, autoimmune condition that it is possible to manage but not cure.

Pityriasis rosea is a skin condition without a known cause. It typically goes away on its own within 2 months.