Psoriatic arthritis (PsA) is a form of arthritis that affects an estimated 30 percent of people with psoriasis. PsA is a chronic autoimmune disease that can, over time, lead to joint inflammation, stiffness, and pain.

About 85 percent of people who have PsA will experience skin symptoms long before their joints are affected. One of the most common symptoms of PsA is a rash — thick red skin covered with flaky white patches.

If you develop symptoms of PsA, it’s important that you seek treatment as soon as possible. This can reduce your risk for joint damage associated with the condition.

Keep reading to learn how to identify a PsA rash, where it may appear, and how to treat it.

PsA rash typically looks the same as psoriasis rash. The most common type of psoriasis rash features raised patches of red skin covered with silvery-white scales. These are called plaques.

Plaques may itch, burn, or hurt. If you have plaques, it's important not to scratch them. Scratching may cause the plaque to thicken or open the skin to infection.

The rash may come and go, and you may have extended periods when you are rash-free. Certain conditions, such as infections, stress, and injuries, may trigger your rash outbreaks.

If you have psoriasis and notice a change in your usual rash pattern or location, see your doctor. This may be a sign of PsA or another underlying condition.

The key difference between a traditional psoriasis rash and PsA rash is the rash location.

PsA rash typically develops on your:

  • elbows
  • knees
  • scalp
  • lower back
  • genitals

However, the rash can appear anywhere on your body, including the palms of your hands and the soles of your feet.

Nail psoriasis, which is commonly associated with PsA, can affect the fingernails and toenails.

Nail psoriasis may cause:

  • pitting
  • discoloration
  • nails to detach from the nail bed (onychosis)
  • tenderness

Learn more: Nail psoriasis »

Your treatment plan will vary based on the type of psoriasis you have and the severity of your rash symptoms. With PsA, your treatment plan will also include drugs to help control arthritis symptoms.

For rash, your doctor may prescribe:

  • creams and ointments to soothe your skin
  • oral drugs to reduce skin cell production
  • light therapy to reduce inflammation

The goal of rash treatment is to reduce plaque formation by stopping the skin cells from growing too quickly and by smoothing your skin.

Topical remedies

Topical medicines can help relieve itchiness, dryness, and inflammation caused by PsA rash.

Depending on the medication, this may be achieved with a:

  • cream
  • gel
  • lotion
  • shampoo
  • spray
  • ointment

These medications are available in both over-the-counter (OTC) and prescription formulas.

Common OTC remedies typically include salicylic acid and coal tar. Prescription treatments generally contain corticosteroids or vitamin derivatives.

Common prescription topicals include:

  • calcitriol, a naturally occurring form of vitamin D-3
  • calcipotriene, a manmade form of vitamin D-3
  • calcipotriene combined with the corticosteroid betamethasone dipropionate
  • tazarotene, a derivative of vitamin A
  • anthralin, a manmade form of the naturally occurring substance chrysarobin

Your treatment plan may involve a combination of OTC and prescription medications. You and your doctor may have to experiment to find what combinations work best for you. Some medications, like corticosteroids, may have side effects for long-term use. Talk with your doctor about the potential benefits and risks associated with each option.

Over-the-counter moisturizers can help calm your skin and counter the itching, but moisturizers alone usually will not heal the plaques.

Learn more: Skin care and psoriasis: What to look for in a lotion »

Oral or injected drugs

There are a variety of drugs that target skin cell production or your immune system. These include:

Corticosteroids: These medications mimic cortisol, a naturally-occurring anti-inflammatory hormone produced by your body. These are normally taken by mouth and can help reduce inflammation. Injected forms can provide temporary inflammation relief.

Long-term use can result in facial swelling and weight gain. It may also increase your risk for osteoporosis.

Disease-modifying antirheumatic drugs (DMARDs): These medications suppress the chemicals in your body that cause inflammation. This can help reduce prevent joint damage. DMARDs are typically taken by mouth.

Biologics, which are a subset of DMARDs: These medications can prevent inflammation on a cellular level. Biologics are typically injected. There are two different types of biologics: anti-tumor necrosis factor-alpha drugs and ustekinumab. Each blocks different proteins within the body.

Your risk for infection may increase while taking biologics, because these work by suppressing your immune system.

Learn more: Injectable medications vs. oral medications for psoriatic arthritis »

Light therapy

Natural or artificial light in controlled amounts can be used to reduce your psoriasis rash.

Common approaches include:

UVB light machine: Exposing your rash to UVB radiation produced by a light machine for small amounts of time a few times a week can help reduce inflammation. Dermatologists often have UVB machines for home use. You can also buy them commercially for home use.

UVA light machine: This approach uses a light machine that produces UVA radiation. When combined with psoralen, a drug that makes your skin more light-sensitive, this method can improve severe psoriasis. This is also known as photochemotherapy.

Excimer laser: An excimer laser, which concentrates more powerful UVB radiation on the psoriasis spots, is a more targeted method to control the rash. This is used in a doctor's office and usually requires fewer sessions than other UV treatments.

Talk with your doctor about whether there are home or in-office sessions are right for you.

Home remedies

Certain lifestyle changes can also help control itching and inflammation.

Tips and tricks

  • Keeping your skin well lubricated is important, especially when the air is dry. You may need to apply a moisturizer a few times a day.
  • Taking warm (not hot) baths is helpful in calming itchy and inflamed skin. Add Epsom salts, colloidal oatmeal, or oils to soak in, and use only mild soaps.
  • Avoiding things that seem to trigger outbreaks, such as stress, alcohol, smoking, or certain fragrances.
  • Eating a healthy diet and getting regular exercise can also benefit your overall well-being.

Psoriasis is a chronic disease, and there's no known cure. It affects every person differently. How fast your rash clears up depends on its severity and the effectiveness of your treatment plan. It may take a while for you and your doctor to work out a combination of treatments that keeps the rash under control. Psoriasis rash usually does clear up and you have a period of remission, but it can flare up again. If you learn to recognize and avoid what triggers flare-ups, you may be able to reduce the frequency of flare-ups.

Keep reading: 10 psoriasis triggers to avoid »

Although rash is a common indicator of PsA, you can develop PsA without having a rash. About 15 percent of people develop PsA without previously having psoriasis. Sometimes, people develop PsA and psoriasis at the same time.

In these situations, it’s important to be aware of what the other symptoms of PsA are.

Although rash is commonly associated with PsA, it isn’t the only symptom.

Other symptoms include:

  • tiredness
  • morning stiffness
  • swelling, pain, or tenderness in joints
  • tendon or ligament pain
  • reduced range of motion in joints
  • nail changes, such as pitting and cracking
  • swollen fingers and toes that look like sausages (dactylitis)
  • eye problems, including redness, irritation, and conjunctivitis

Symptoms and their severity vary from person to person. Many symptoms mimic those of other diseases, such as osteoarthritis, rheumatoid arthritis, and gout.

If you’re experiencing symptoms, be sure to talk with your doctor. Getting a diagnosis as soon as possible can help improve your quality of life by managing symptoms and reduce your risk for long-term complications.