Psoriasis: Why Do Scaly Patches Appear, and What Treatments Exist?

Scaly patches that appear and return are often plaque psoriasis, a long-term condition in which the immune system speeds up skin cell turnover, so cells build up as thick, silvery-white scale over red or darker skin. Several factors contribute, including genes and triggers such as stress or skin injury. This article explains how psoriasis is diagnosed, which treatments exist, and which symptoms need prompt medical attention.

What psoriasis is

Psoriasis is a chronic condition driven by the immune system. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), immune signaling in the skin leads to skin cells maturing and piling up much faster than usual. The result is raised, well-defined patches called plaques.

It is not contagious. You cannot catch it from someone else or pass it on by touch. It can come and go over time, with flares followed by quieter periods.

Why the patches form

The mechanism is not fully understood, but several factors seem to work together.

• Immune activity: overactive immune cells release signaling proteins that inflame the skin and speed up cell growth.
• Genetics: psoriasis often runs in families, though having a relative with it does not mean you will develop it.
• Environment: some people notice flares after certain triggers.

Triggers reported by many people include skin injury (scrapes, sunburn, tattoos), infections such as strep throat, stress, cold dry weather, smoking, heavy alcohol use, and certain medicines. Tell your clinician about every medicine you take, because some, such as lithium, beta-blockers, and stopping oral steroids abruptly, have been linked to flares. They can decide whether any change is appropriate. Never stop a prescription without your prescriber's advice.

What it looks like: the main types

Plaque psoriasis

This is the most familiar form. Plaques are often found on the elbows, knees, scalp, and lower back. They can itch, burn, crack, or sting. On lighter skin they often look pink or red with silvery scale. On brown and Black skin they may look purple, gray, or darker brown, so color alone can be misleading.

Other forms

• Guttate: many small drop-shaped spots, sometimes after a throat infection.
• Inverse: smooth red patches in skin folds such as the armpits or groin.
• Pustular: white pus-filled bumps that are not infectious, on the palms and soles or more widely.
• Erythrodermic: widespread redness across much of the body. This is uncommon and can be dangerous.
• Nail and scalp psoriasis: pitting, lifting, or discoloration of nails, and scale that can extend past the hairline.

How psoriasis is diagnosed

Clinicians combine your history, family history, and a skin examination. Sometimes a small skin sample (biopsy) is taken when the appearance is unclear. There is no single blood test for typical psoriasis. Conditions that can look similar include eczema, fungal infection, and seborrheic dermatitis. For another red facial condition, see our article on rosacea versus acne.

Treatment options

Treatment depends on how much skin is involved, where it is, how much it affects daily life, and whether joints are affected. Dermatology organizations publish guidelines of care for psoriasis in adults, with separate sections on topical therapy, phototherapy, and systemic and biologic treatment; outcomes vary between people.

Skin care and topical treatments

• Moisturizers: thick, fragrance-free ointments or creams can reduce dryness and itch.
• Topical corticosteroids: often used for plaques; strength, body site, and duration should be set by a clinician, because prolonged or heavy use can thin the skin, especially on the face and folds.
• Vitamin D analogs, topical retinoids, calcineurin inhibitors, and newer non-steroid creams: options your clinician may use alone or combined.
• Salicylic acid and coal tar products: may help soften scale, especially on the scalp.

Light therapy

Controlled ultraviolet light (phototherapy) given in a clinic can help many people with more widespread disease. Tanning beds are not a substitute and raise skin cancer risk. Clinic phototherapy is dosed and supervised because it also carries burn and skin cancer risks, and your clinician will weigh it against any history of skin cancer and any light-sensitizing medicines you take.

Oral and injected medicines

For moderate to severe disease, clinicians may consider oral medicines such as methotrexate, cyclosporine, or apremilast, or biologic medicines that block specific immune signals. These drugs act on the immune system, so they may raise infection risk and usually need screening and monitoring. Methotrexate and cyclosporine carry FDA boxed warnings (for example liver, bone marrow, and pregnancy risks with methotrexate; kidney effects and high blood pressure with cyclosporine), and biologics need infection screening, so your prescriber will set up lab work and check-ins. Do not change timing or doses on your own, and tell your prescriber right away if you could be or plan to become pregnant.

Psoriatic arthritis and other health links

Psoriatic arthritis is a form of inflammatory arthritis that can occur in people with psoriasis, and joint symptoms can sometimes appear before or without notable skin changes. Warning signs include joint pain or swelling, morning stiffness, a swollen "sausage-like" finger or toe, heel pain, and nail changes. Early evaluation may help protect joints. Our article on morning stiffness in arthritis explains how inflammatory stiffness differs from wear-and-tear arthritis.

According to NIAMS, psoriasis is associated with higher rates of cardiovascular risk factors, such as high blood pressure, obesity, and diabetes, as well as depression and anxiety. These links do not mean everyone with psoriasis will develop these conditions, but they are reasons to keep up with routine checkups.

Everyday habits that may help

• Moisturize regularly, especially after bathing, using lukewarm rather than hot water.
• Avoid picking or scratching, since skin injury can sometimes cause new plaques.
• Protect skin from sunburn, while asking your clinician about safe, limited sun exposure.
• If you smoke or drink alcohol heavily, discuss support with your clinician, since both are associated with worse disease.
• Track flares and possible triggers to share at visits.

Living with visible skin disease can affect mood and confidence. If you feel persistently low or hopeless, tell your clinician. If you ever have thoughts of harming yourself, call or text 988, the Suicide and Crisis Lifeline, or call 911 if you are in immediate danger.

When to see a clinician

See a clinician for any new scaly patch that persists, for plaques that are spreading or not responding to over-the-counter care, for joint symptoms, and for signs of skin infection such as warmth, pus, or spreading redness. Red skin that is spreading across most of the body needs same-day medical evaluation. Go to the emergency room if it comes with fever, chills, a fast heartbeat, confusion, or faintness, as described in the box below.

When to Seek Medical Care