Psoriasis is a persistent, long-lasting (chronic) disease. Psoriasis is a common skin disease that affects the life cycle of skin cells. Normally, new cells take about a month to move from the lowest skin layer where they’re produced, to the outermost layer where they die and flake off. With psoriasis, the entire life cycle takes only days. As a result, cells build up rapidly, forming thick silvery scales and itchy, dry, red patches that are sometimes painful. For some people, psoriasis is just a nuisance. For others, it’s disabling, especially when associated with arthritis. No cure exists, but psoriasis treatments may offer significant relief. And self-care measures, such as using a nonprescription cortisone cream and exposing your skin to small amounts of ultraviolet light, can improve your psoriasis symptoms.
The cause of psoriasis is related to the immune system, and more specifically, a type of white blood cell called a T lymphocyte or T cell. Normally, T cells travel throughout the body to detect and fight off foreign substances, such as viruses or bacteria. In people with psoriasis, however, the T cells attack healthy skin cells by mistake as if to heal a wound or to fight an infection. Overactive T cells trigger other immune responses that cause an increased production of both healthy skin cells and more T cells. What results is an ongoing cycle in which new skin cells move to the outermost layer of skin too quickly — in days rather than weeks. Dead skin and white blood cells can’t slough off quickly enough and build up in thick, scaly patches on the skin’s surface. This usually doesn’t stop unless treatment interrupts the cycle. Just what causes T cells to malfunction in people with psoriasis isn’t entirely clear, although researchers think genetic and environmental factors both play a role.
Psoriasis typically starts or worsens because of a trigger that you may be able to identify and avoid. Factors that may trigger psoriasis include:
- Infections, such as strep throat or thrush
- Injury to the skin, such as a cut or scrape, bug bite, or a severe sunburn
- Cold weather
- Heavy alcohol consumption
- Certain medications, including lithium, which is prescribed for bipolar disorder, high blood pressure medications such as beta blockers, antimalarial drugs and iodides
Psoriasis symptoms can vary from person to person but may include one or more of the following:
- Red patches of skin covered with silvery scales
- Small scaling spots (commonly seen in children)
- Dry, cracked skin that may bleed
- Itching, burning or soreness
- Thickened, pitted or ridged nails
- Swollen and stiff joints
Psoriasis patches can range from a few spots of dandruff-like scaling to major eruptions that cover large areas. Mild cases of psoriasis may be a nuisance. But more severe cases can be painful, disfiguring and disabling.
Most types of psoriasis go through cycles, flaring for a few weeks or months, then subsiding for a time or even going into complete remission. In most cases, however, the disease eventually returns.
Several types of psoriasis exist. These include:
Plaque psoriasis. The most common form, plaque psoriasis causes dry, red skin lesions (plaques) covered with silvery scales. The plaques itch or feel sore and may occur anywhere on your body, including your genitals and the soft tissue inside your mouth. You may have just a few plaques or many, and in severe cases, the skin around your joints may crack and bleed.
Nail psoriasis. Psoriasis can affect fingernails and toenails, causing pitting, abnormal nail growth and discoloration. Psoriatic nails may become loose and separate from the nail bed (onycholysis). Severe cases may cause the nail to crumble.
Scalp psoriasis. Psoriasis on the scalp appears as red, itchy areas with silvery-white scales. You may notice flakes of dead skin in your hair or on your shoulders, especially after scratching your scalp.
Guttate psoriasis. This primarily affects people younger than 30 and is usually triggered by a bacterial infection such as strep throat. It’s marked by small, water-drop-shaped sores on your trunk, arms, legs and scalp. The sores are covered by a fine scale and aren’t as thick as typical plaques are. You may have a single outbreak that goes away on its own, or you may have repeated episodes, especially if you have ongoing respiratory infections.
Inverse psoriasis. Mainly affecting the skin in the armpits, groin, under the breasts and around the genitals, inverse psoriasis causes smooth patches of red, inflamed skin. It’s more common in overweight people and is worsened by friction and sweating.
Pustular psoriasis. This rare form of psoriasis can occur in widespread patches (generalized pustular psoriasis) or in smaller areas on your hands, feet or fingertips. It generally develops quickly, with pus-filled blisters appearing just hours after your skin becomes red and tender. The blisters dry within a day or two but may reappear every few days or weeks. Generalized pustular psoriasis can also cause fever, chills, severe itching, weight loss and fatigue.
Erythrodermic psoriasis. The least common type of psoriasis, erythrodermic psoriasis can cover your entire body with a red, peeling rash that can itch or burn intensely. It may be triggered by severe sunburn, by corticosteroids and other medications, or by another type of psoriasis that’s poorly controlled.
Most often, psoriasis can be diagnosed with a visual exam. Sometimes, however, your doctor may take a small sample of skin (biopsy) that’s examined under a microscope to determine the exact type of psoriasis and to rule out other disorders. These include:
- Seborrheic dermatitis. This type of dermatitis is characterized by greasy, scaly, itchy, red skin. It’s often found on oily areas of the body, such as the face, upper chest and back. Seborrheic dermatitis can also appear on the scalp as stubborn, itchy dandruff.
- Lichen planus. This is an inflammatory skin condition that appears as rows of itchy, flat-topped bumps (lesions) on the arms and legs. The rash can last months or even years and may reappear after it goes away.
- Neurodermatitis. Also called lichen simplex chronicus, neurodermatitis occurs because of repeated scratching. Chronic scratching can cause patches of thickened, brownish skin. These patches have definite margins that are thick and leather-like (lichenified). Typically, neurodermatitis occurs on the scalp, neck, wrist, upper forearm and ankle.
- Pityriasis rosea. This common skin condition usually begins as one large spot on your chest, abdomen or back (herald patch) which then spreads. The rash of pityriasis rosea often sweeps out from the middle of the body, and its shape resembles drooping pine-tree branches.
Psoriasis treatments aim to interrupt the cycle that causes an increased production of skin cells, thereby reducing inflammation and plaque formation. Other treatments, especially those you apply to your skin (topical treatments), help remove scale and smooth the skin. Although doctors choose treatments based on the type and severity of psoriasis and the areas of skin affected, the traditional approach is to start with the mildest treatments — topical creams and ultraviolet light therapy (phototherapy) — and then progress to stronger ones if necessary. The goal is to find the most effective way to slow cell turnover with the fewest possible side effects. In spite of a wide range of options, psoriasis treatment can be challenging. The disease is unpredictable, going through cycles of improvement and worsening seemingly at whim. Effects of psoriasis treatments also can be unpredictable; what works well for one person might be ineffective for someone else. Your skin can also become resistant to various treatments over time, and the most potent psoriasis treatments can have serious side effects.
Psoriasis treatments can be divided into three main types: topical treatments, light therapy and oral medications.
Used alone, creams and ointments that you apply to your skin can effectively treat mild to moderate psoriasis. When skin disease is more severe, creams are likely to be combined with oral medications or phototherapy. Topical psoriasis treatments include:
- Topical corticosteroids. These powerful anti-inflammatory drugs are the most frequently prescribed medications for treating mild to moderate psoriasis. They slow cell turnover by suppressing the immune system, which reduces inflammation and relieves associated itching. Topical corticosteroids range in strength, from mild to very strong. Low-potency corticosteroid ointments are usually recommended for sensitive areas such as your face and for treating widespread patches of damaged skin. Your doctor may prescribe stronger corticosteroid ointment for small areas of your skin, for stubborn plaques on your hands or feet, or when other treatments fail. To minimize side effects and to increase effectiveness, topical corticosteroids are generally used on active outbreaks until they’re under control.
- Vitamin D analogues. These synthetic forms of vitamin D reduce skin inflammation and help prevent skin cells from reproducing. Calcipotriene (Dovonex) is a prescription cream, ointment or solution containing a vitamin D analogue that may be used alone to treat mild to moderate psoriasis or in combination with other topical medications or phototherapy.
- Anthralin. This medication is believed to normalize DNA activity in skin cells and to reduce inflammation. Anthralin (Dritho-Scalp or Psoriatec) can remove scale and smooth skin, but it stains virtually anything it touches, including skin, clothing, countertops and bedding. For that reason doctors often recommend short-contact treatment — allowing the cream to stay on your skin for a brief time before washing it off. Anthralin is sometimes used in combination with ultraviolet light.
- Topical retinoids. These are commonly used to treat acne and sun-damaged skin, but tazarotene (Tazorac) was developed specifically for the treatment of psoriasis. Like other vitamin A derivatives, it normalizes DNA activity in skin cells. The most common side effect is skin irritation. Although the risk of birth defects is far lower for topical retinoids than for oral retinoids, your doctor needs to know if you’re pregnant or intend to become pregnant if you’re using tazarotene.
- Calcineurin inhibitors. Currently, calcineurin inhibitors (tacrolimus and pimecrolimus) are only approved for the treatment of atopic dermatitis, but studies have shown them to be effective at times in the treatment of psoriasis as well. Calcineurin inhibitors are thought to disrupt the activation of T cells, which in turn reduces inflammation and plaque buildup. Calcineurin inhibitors are not recommended for long-term or continuous use because of a potential increased risk of skin cancer and lymphoma.
- Coal tar. A thick, black byproduct of the manufacture of gas and coke, coal tar is probably the oldest treatment for psoriasis. It reduces scaling, itching and inflammation. Exactly how it works isn’t known. Coal tar has few known side effects, but it’s messy, stains clothing and bedding, and has a strong odor.
- Moisturizers. By themselves, moisturizing creams won’t heal psoriasis, but they can reduce itching and scaling and can help combat the dryness that results from other therapies. Moisturizers in an ointment base are usually more effective than are lighter creams and lotions.
Light therapy (phototherapy)
As the name suggests, this psoriasis treatment uses natural or artificial light. The simplest and easiest form of phototherapy involves exposing your skin to controlled amounts of natural sunlight. Other forms of light therapy include the use of artificial ultraviolet A (UVA) or ultraviolet B (UVB) light either alone or in combination with medications.
- Sunlight. Ultraviolet (UV) light is a wavelength of light in a range too short for the human eye to see. When exposed to UV rays in sunlight or artificial light, the activated T cells in the skin die. This slows skin cell turnover and reduces scaling and inflammation. Brief, daily exposures to small amounts of sunlight may improve psoriasis, but intense sun exposure can worsen symptoms can cause skin damage. Before beginning a sunlight regimen, ask your doctor about the safest way to use natural sunlight for psoriasis treatment.
- UVB phototherapy. Controlled doses of UVB light from an artificial light source may improve mild to moderate psoriasis symptoms. UVB phototherapy, also called broadband UVB, can be used to treat single patches, widespread psoriasis and psoriasis that resists topical treatments.
- Narrowband UVB therapy. A newer type of psoriasis treatment, narrowband UVB therapy may be more effective than broadband UVB treatment. It’s usually administered two or three times a week until the skin improves, then maintenance may require only weekly sessions. Narrowband UVB therapy may cause more severe and longer-lasting burns, however.
- Photochemotherapy, or psoralen plus ultraviolet A (PUVA). Photochemotherapy involves taking a light-sensitizing medication (psoralen) before exposure to UVA light. UVA light penetrates deeper into the skin than does UVB light, and psoralen makes the skin more sensitive to the effects of UVA exposure. This more aggressive treatment consistently improves skin and is often used for more severe cases of psoriasis. PUVA involves two or three treatments a week for a prescribed number of weeks. Short-term side effects include nausea, headache, burning and itching. Long-term treatment increases your risk of skin cancer, including melanoma, the most serious form of skin cancer.
- Excimer laser. This form of light therapy, used for mild to moderate psoriasis, treats only the involved skin. A controlled beam of UVB light is aimed at the psoriasis plaques to control scaling and inflammation. Healthy skin surrounding the patches remains undamaged. Excimer laser therapy requires fewer sessions than does traditional phototherapy because more powerful UVB light is used. Side effects can include redness and blistering.
- Combination light therapy. Combining UV light with other treatments such as retinoids frequently improves phototherapy’s effectiveness. Combination therapies are often used after other phototherapy options are ineffective. Some doctors give UVB treatment in conjunction with coal tar, called the Goeckerman treatment. The two therapies together are more effective than either alone because coal tar makes skin more receptive to UVB light. Another method, the Ingram regimen, combines UVB therapy with a coal tar bath and an anthralin-salicylic acid paste that’s left on your skin for several hours or overnight.
If you have severe psoriasis or it’s resistant to other types of treatment, your doctor may prescribe oral or injected drugs. Because of severe side effects, some of these medications are used for just brief periods of time and may be alternated with other forms of treatment.
- Retinoids. Related to vitamin A, this group of drugs may reduce the production of skin cells in people with severe psoriasis who don’t respond to other therapies. Signs and symptoms usually return once therapy is discontinued, however. And because retinoids such as acitretin (Soriatane) can cause severe birth defects, women must avoid pregnancy for at least three years after taking the medication.
- Methotrexate. Taken orally, methotrexate helps psoriasis by decreasing the production of skin cells, suppressing inflammation and reducing the release of histamine — a substance involved in allergic reactions. It may also slow the progression of arthritis in some people with psoriatic arthritis. Methotrexate is generally well tolerated in low doses, but when used for long periods it can cause a number of serious side effects, including severe liver damage and decreased production of red and white blood cells and platelets. Taking 1 milligram of folic acid on a daily basis may help reduce some of the common side effects associated with methotrexate.
- Azathioprine. A potent anti-inflammatory drug, azathioprine may be used to treat severe psoriasis when other treatment options fail. Taken long term, azathioprine increases the risk of developing cancerous or noncancerous growths (neoplasias) and certain blood disorders. Other potential side effects include nausea and vomiting, bruising more easily than normal, and fatigue.
- Cyclosporine. Cyclosporine works by suppressing the immune system and is similar to methotrexate in effectiveness. Like other immunosuppressant drugs, cyclosporine increases your risk of infection and other health problems, including cancer. Cyclosporine also makes you more susceptible to kidney problems and high blood pressure — the risk increases with higher dosages and long-term therapy.
- Hydroxyurea. This medication isn’t as effective as cyclosporine or methotrexate, but unlike the stronger drugs it can be used with phototherapy treatments. Possible side effects include anemia and a decrease in white blood cells and platelets. It should not be taken by women who are pregnant or planning to become pregnant.
- Immunomodulator drugs (biologics). Several immunomodulator drugs are approved for the treatment of moderate to severe cases of psoriasis. They include alefacept (Amevive), efalizumab (Raptiva), etanercept (Enbrel) and infliximab (Remicade). These drugs are given by intravenous infusion, intramuscular injection or subcutaneous injection and are usually used for people who have failed to respond to traditional therapy or for people with associated psoriatic arthritis. Biologics work by blocking interactions between certain immune system cells. Although they’re derived from natural sources rather than chemical ones, they have strong effects on the immune system and likely pose many of the same risks as other immunosuppressant drugs.