Psoriasis is one of the most common skin conditions in the world. The condition, characterized by raised plaques of inflamed, red skin and white scales that can “flake off,” affects people of all ages—even infants. Globally, somewhere between 2 and 3% of the population has psoriasis, and according to some estimates, nearly 5% of Americans live with this skin condition.

For many, psoriasis is a relatively mild condition that doesn’t interfere with life. Their raised, red plaques of skin may be limited to just a small area on the body and may not cause any itching or tenderness. But for others, psoriasis is anything but mild. These patients have large areas of inflamed, flaky skin. The most common areas impacted by psoriasis are the elbows and knees, but plaques may appear anywhere on the body including the scalp, hands, feet, and face.

People with psoriasis may experience severe itching and discomfort, including emotional distress, due to their appearance. For them, it’s helpful to know that many treatments are available that can help control the skin rash and reduce symptoms.

“There have been many recent advances in the treatment of psoriasis, and more new medications are under study,” says Yale Medicine dermatologist Jeffrey Cohen, MD. “With these new treatments, we are able to effectively treat most patients, even people with severe psoriasis that covers large areas of the body. In fact, with treatment, many patients will have very few or even no psoriasis plaques on their skin.”

Psoriasis is a common, long-term skin condition characterized by raised plaques of inflamed, red skin. These plaques, are often, but not always, covered with silvery-white scales that tend to flake off. Plaques can form on any part of the body, but they most often affect the elbows, knees, hands, feet, back, and scalp. They can vary in size and may be itchy or painful. 

Psoriasis can affect people of any age, but it has two peak times of onset, one between ages 20 and 30 and the other between ages 50 and 60. Though it is often thought of as a condition that only affects the skin, people with psoriasis are at increased risk for several other medical problems including cardiovascular disease as well as for a condition called psoriatic arthritis, which affects the joints.

Plaque psoriasis is the most common type, accounting for around 90% of all cases. It is characterized by red, scaly plaques that most frequently affect the scalp, knees, lower back, hands, and feet.

There are several other types of psoriasis, which together make up about 10% of cases. These include:

• Guttate psoriasis most often affects children and adolescents, though it can develop in adults. This type of psoriasis may involve small, reddish, white-scaled spots on the chest, abdomen, arms, and/or thighs. This form of psoriasis can be associated with strep infections.
• Inverse psoriasis usually affects the armpits, groin, genitals, and skin under the breast. It appears as smooth, shiny, red areas of skin, often without scales.
• Pustular psoriasis can be localized, which means it can occur on a specific part of the skin (often the hands and feet) or it may be generalized (present across large areas of the body). The generalized form can be accompanied by fever, hypocalcemia (low levels of calcium in the blood), acute respiratory distress syndrome (ARDS), and sepsis. Because of these complications, generalized pustular psoriasis can be life-threatening. 
• Erythrodermic Psoriasis is a rare but severe type of psoriasis in which red, itchy, scaly skin develops over most of or even the entire body. It can be accompanied by fever, chills, shivering, dehydration, and infection.

In some cases, psoriasis affects the nails, resulting in thickening, pitting (divots), discoloration, and separation of nails from the nail bed.

At its core, psoriasis is caused by the activity of the immune system. The immune system in the skin is over-active in psoriasis and cells produce messaging signals—called cytokines—that tell the skin to form itchy red plaques. A cycle of communication occurs between cells of the immune system in the skin that prompts psoriasis to continue. Many of the most effective treatments for psoriasis specifically target the cytokines, which are most important in the development of psoriasis.

Scientists do not yet know what causes the immune system to attack healthy cells in people who have psoriasis. It is clear, though, that the condition has a genetic component and that people with a family history of psoriasis are at higher risk for the disease. It is also believed that certain aspect of a person’s environment can also increase the risk of psoriasis.

Other factors can cause flare-ups of symptoms. While they do not cause psoriasis, these factors can trigger and worsen symptoms. These include:

• Alcohol consumption
• Obesity
• Smoking
• Certain medications, including lithium, beta-blockers, and antimalarial drugs
• Stress
• Infections such as HIV and strep throat
• Sunburn
• Skin injuries

Psoriasis is not contagious.

Symptoms caused by psoriasis include:

• Inflamed, red or salmon-colored plaques of skin, often covered with flaky, silvery-white scales
• Plaques may appear on any part of the body, including the scalp, palms, and soles of the feet. The most commonly affected areas are the knees, elbows, scalp, hands, feet, and back.
• Dry, itchy, and/or sore skin
• If plaques are scratched or picked off, pinpoint bleeding may occur
• Thickened and pitted nails; nails may separate from the nail bed
• Joint and/or spine stiffness, swelling, and pain

Symptoms tend to fluctuate, with periods of absence—or lessening—of symptoms interspersed with episodes of relapse or increased severity.

To diagnose psoriasis, your doctor will ask about your family and medical history and conduct a physical exam to look at your skin. This is usually enough for doctors to make a diagnosis. Sometimes, though, additional tests are necessary. Your doctor may perform biopsy, a procedure in which he or she removes a small piece of affected skin for laboratory analysis. If you have joint pain or swelling, an X-ray can help determine if you have psoriatic arthritis.

Though there is no cure for psoriasis, many treatment options are available. These treatments all aim to reduce symptoms and prevent flare-ups.

Psoriasis treatment falls into four broad categories:

Topical treatments. Ointments, creams, lotions, gels, and shampoos are frequently used to treat psoriasis.

• Moisturizers. Over-the-counter moisturizers can help relieve itchy skin.
• Topical corticosteroids. Steroid ointments, creams, lotions, and shampoos can reduce inflammation, itching, and soreness. Hydrocortisone creams are available over the counter. More potent medications are available by prescription.
• Vitamin D analogs. They may be used alone or in combination with a topical corticosteroid. Calcipotriene is often used to treat plaque psoriasis.
• Tazarotene. This medication is often used to treat mild to moderate psoriasis.
• Calcineurin inhibitor. These medications are often used to treat psoriasis that affects the face or genitals.
• Tar. Topical treatments containing coal tar can reduce inflammation and itching. They may be used in conjunction with a topical corticosteroid or with phototherapy. It's important to note, however, that tar is no longer commonly used to treat psoriasis.

Oral medications.

• Methotrexate. Used to treat moderate to severe psoriasis, methotrexate reduces inflammation caused by psoriasis. 
• Cyclosporine. This medication suppresses the immune system and reduces inflammation caused by psoriasis. It is used to treat severe psoriasis and is often a temporary treatment to quickly control the problem.
• Retinoids. People with severe psoriasis may be prescribed a retinoid (a medication derived from vitamin A) called acitretin.
• Acitretin. This medication blocks an immune signal that is important for psoriasis. 

Biologic Treatments. These are injectable medications that target immune cells that play a role in psoriasis. They are usually used to treat moderate to severe psoriasis.  

Phototherapy. Exposing the skin to specific wavelengths of ultraviolet light can reduce inflammation. It is usually used to treat moderate to severe psoriasis.    

Psoriasis is usually a lifelong condition marked by periods of remission and exacerbation of symptoms. While it is best known for its characteristic plaques of inflamed skin, up to 40% of people who have psoriasis develop psoriatic arthritis. Fortunately, many treatments that can reduce symptoms and limit flare ups are available.

“We approach the treatment of psoriasis in a very personalized way, and recommend treatments based on the way a person’s skin looks in addition to details about his or her medical history and other medical problems and personal preferences about treatment,” says Dr. Cohen. “By considering all of these relevant factors, we are able to work with patients to develop a treatment plan that they are comfortable and satisfied with. We are also actively involved in research on the most advanced treatments for psoriasis to help improve treatment for our patients and for those all over the world. Most importantly, we treat each patient as we would want a member of our own families to be treated.”