On this page:
Psoriasis is a chronic (long-lasting) skin disease of scaling and inflammation
that affects 2 to 2.6 percent of the United States population, or between 5.8
and 7.5 million people. Although the disease occurs in all age groups, it primarily
affects adults. It appears about equally in males and females. Psoriasis occurs
when skin cells quickly rise from their origin below the surface of the skin
and pile up on the surface before they have a chance to mature. Usually this
movement (also called turnover) takes about a month, but in psoriasis it may
occur in only a few days. In its typical form, psoriasis results in patches
of thick, red (inflamed) skin covered with silvery scales. These patches, which
are sometimes referred to as plaques, usually itch or feel sore. They most
often occur on the elbows, knees, other parts of the legs, scalp, lower back,
face, palms, and soles of the feet, but they can occur on skin anywhere on
The disease may also affect the fingernails, the toenails, and the soft tissues
of the genitals and inside the mouth. While it is not unusual for the skin
around affected joints to crack, approximately 1 million people with psoriasis
experience joint inflammation that produces symptoms of arthritis. This condition
is called psoriatic arthritis.
Return to top
Individuals with psoriasis may experience significant physical discomfort
and some disability. Itching and pain can interfere with basic functions, such
as self-care, walking, and sleep. Plaques on hands and feet can prevent individuals
from working at certain occupations, playing some sports, and caring for family
members or a home. The frequency of medical care is costly and can interfere
with an employment or school schedule. People with moderate to severe psoriasis
may feel self-conscious about their appearance and have a poor self-image that
stems from fear of public rejection and psychosexual concerns. Psychological
distress can lead to significant depression and social isolation.
Return to top
Psoriasis is a skin disorder driven by the immune system, especially involving
a type of white blood cell called a T cell. Normally, T cells help protect
the body against infection and disease. In the case of psoriasis, T cells are
put into action by mistake and become so active that they trigger other immune
responses, which lead to inflammation and to rapid turnover of skin cells.
In about one-third of the cases, there is a family history of psoriasis. Researchers
have studied a large number of families affected by psoriasis and identified
genes linked to the disease. (Genes govern every bodily function and determine
the inherited traits passed from parent to child.) People with psoriasis may
notice that there are times when their skin worsens, then improves. Conditions
that may cause flareups include infections, stress, and changes in climate
that dry the skin. Also, certain medicines, including lithium and betablockers,
which are prescribed for high blood pressure, may trigger an outbreak or worsen
Return to top
Occasionally, doctors may find it difficult to diagnose psoriasis, because
it often looks like other skin diseases. It may be necessary to confirm a diagnosis
by examining a small skin sample under a microscope. There are several forms
of psoriasis. Some of these include:
Plaque psoriasis--Skin lesions are red at the base and
covered by silvery scales.
Guttate psoriasis--Small, drop-shaped lesions appear
on the trunk, limbs, and scalp. Guttate psoriasis is most often triggered
by upper respiratory infections (for example, a sore throat caused by streptococcal
Pustular psoriasis--Blisters of noninfectious pus appear
on the skin. Attacks of pustular psoriasis may be triggered by medications,
infections, stress, or exposure to certain chemicals.
Inverse psoriasis--Smooth, red patches occur in the folds
of the skin near the genitals, under the breasts, or in the armpits. The
symptoms may be worsened by friction and sweating.
Erythrodermic psoriasis--Widespread reddening and scaling
of the skin may be a reaction to severe sunburn or to taking corticosteroids
(cortisone) or other medications. It can also be caused by a prolonged
period of increased activity of psoriasis that is poorly controlled.
Psoriatic arthritis--Joint inflammation that produces
symptoms of arthritis in patients who have or will develop psoriasis.
Return to top
Doctors generally treat psoriasis in steps based on the severity of the disease,
size of the areas involved, type of psoriasis, and the patient's response to
initial treatments. This is sometimes called the "1-2-3" approach. In step
1, medicines are applied to the skin (topical treatment). Step 2 uses light
treatments (phototherapy). Step 3 involves taking medicines by mouth or injection
that treat the whole immune system (called systemic therapy).
Over time, affected skin can become resistant to treatment, especially when
topical corticosteroids are used. Also, a treatment that works very well in
one person may have little effect in another. Thus, doctors often use a trial-and-error
approach to find a treatment that works, and they may switch treatments periodically
(for example, every 12 to 24 months) if a treatment does not work or if adverse
Treatments applied directly to the skin may improve its condition. Doctors
find that some patients respond well to ointment or cream forms of corticosteroids,
vitamin D3, retinoids, coal tar, or anthralin. Bath solutions and moisturizers
may be soothing, but they are seldom strong enough to improve the condition
of the skin. Therefore, they usually are combined with stronger remedies.
Corticosteroids--These drugs reduce inflammation and
the turnover of skin cells, and they suppress the immune system. Available
in different strengths, topical corticosteroids (cortisone) are usually
applied to the skin twice a day. Short-term treatment is often effective
in improving, but not completely eliminating, psoriasis. Long-term use
or overuse of highly potent (strong) corticosteroids can cause thinning
of the skin, internal side effects, and resistance to the treatment's benefits.
If less than 10 percent of the skin is involved, some doctors will prescribe
a high-potency corticosteroid ointment. High-potency corticosteroids may
also be prescribed for plaques that don't improve with other treatment,
particularly those on the hands or feet. In situations where the objective
of treatment is comfort, medium-potency corticosteroids may be prescribed
for the broader skin areas of the torso or limbs. Low-potency preparations
are used on delicate skin areas. (Note: Brand names for the different strengths
of corticosteroids are too numerous to list in this booklet.)
Calcipotriene--This drug is a synthetic form of vitamin
D3 that can be applied to the skin. Applying calcipotriene ointment twice
a day controls the speed of turnover of skin cells. Because calcipotriene
can irritate the skin, however, it is not recommended for use on the face
or genitals. It is sometimes combined with topical corticosteroids to reduce
irritation. Use of more than 100 grams of calcipotriene per week may raise
the amount of calcium in the body to unhealthy levels.
Retinoid--Topical retinoids are synthetic forms of vitamin
A. The retinoid tazarotene (Tazorac) is available as a gel or cream that
is applied to the skin. If used alone, this preparation does not act as
quickly as topical corticosteroids, but it does not cause thinning of the
skin or other side effects associated with steroids. However, it can irritate
the skin, particularly in skin folds and the normal skin surrounding a
patch of psoriasis. It is less irritating and sometimes more effective
when combined with a corticosteroid. Because of the risk of birth defects,
women of childbearing age must take measures to prevent pregnancy when
Coal tar--Preparations containing coal tar (gels and
ointments) may be applied directly to the skin, added (as a liquid) to
the bath, or used on the scalp as a shampoo. Coal tar products are available
in different strengths, and many are sold over the counter (not requiring
a prescription). Coal tar is less effective than corticosteroids and many
other treatments and, therefore, is sometimes combined with ultraviolet
B (UVB) phototherapy for a better result. The most potent form of coal
tar may irritate the skin, is messy, has a strong odor, and may stain the
skin or clothing. Thus, it is not popular with many patients.
Anthralin--Anthralin reduces the increase in skin cells
and inflammation. Doctors sometimes prescribe a 15- to 30-minute application
of anthralin ointment, cream, or paste once each day to treat chronic psoriasis
lesions. Afterward, anthralin must be washed off the skin to prevent irritation.
This treatment often fails to adequately improve the skin, and it stains
skin, bathtub, sink, and clothing brown or purple. In addition, the risk
of skin irritation makes anthralin unsuitable for acute or actively inflamed
Salicylic acid--This peeling agent, which is available
in many forms such as ointments, creams, gels, and shampoos, can be applied
to reduce scaling of the skin or scalp. Often, it is more effective when
combined with topical corticosteroids, anthralin, or coal tar.
Clobetasol propionate--This is a foam topical medication
(Olux), which has been approved for the treatment of scalp and body psoriasis.
The foam penetrates the skin very well, is easy to use, and is not as messy
as many other topical medications.
Bath solutions--People with psoriasis may find that adding
oil when bathing, then applying a moisturizer, soothes their skin. Also,
individuals can remove scales and reduce itching by soaking for 15 minutes
in water containing a coal tar solution, oiled oatmeal, Epsom salts, or
Dead Sea salts.
Moisturizers--When applied regularly over a long period,
moisturizers have a soothing effect. Preparations that are thick and greasy
usually work best because they seal water in the skin, reducing scaling
Natural ultraviolet light from the sun and controlled delivery of artificial
ultraviolet light are used in treating psoriasis.
Sunlight--Much of sunlight is composed of bands of different
wavelengths of ultraviolet (UV) light. When absorbed into the skin, UV
light suppresses the process leading to disease, causing activated T cells
in the skin to die. This process reduces inflammation and slows the turnover
of skin cells that causes scaling. Daily, short, nonburning exposure to
sunlight clears or improves psoriasis in many people. Therefore, exposing
affected skin to sunlight is one initial treatment for the disease.
Ultraviolet B (UVB) phototherapy--UVB is light with a
short wavelength that is absorbed in the skin's epidermis. An artificial
source can be used to treat mild and moderate psoriasis. Some physicians
will start treating patients with UVB instead of topical agents. A UVB
phototherapy, called broadband UVB, can be used for a few small lesions,
to treat widespread psoriasis, or for lesions that resist topical treatment.
This type of phototherapy is normally given in a doctor's office by using
a light panel or light box. Some patients use UVB light boxes at home under
a doctor's guidance.
A newer type of UVB, called narrowband UVB, emits the part of the ultraviolet
light spectrum band that is most helpful for psoriasis. Narrowband UVB
treatment is superior to broadband UVB, but it is less effective than PUVA
treatment (see next paragraph). It is gaining in popularity because it
does help and is more convenient than PUVA. At first, patients may require
several treatments of narrowband UVB spaced close together to improve their
skin. Once the skin has shown improvement, a maintenance treatment once
each week may be all that is necessary. However, narrowband UVB treatment
is not without risk. It can cause more severe and longer lasting burns
than broadband treatment.
Psoralen and ultraviolet A phototherapy (PUVA)--This
treatment combines oral or topical administration of a medicine called
psoralen with exposure to ultraviolet A (UVA) light. UVA has a long wavelength
that penetrates deeper into the skin than UVB. Psoralen makes the skin
more sensitive to this light. PUVA is normally used when more than 10 percent
of the skin is affected or when the disease interferes with a person's
occupation (for example, when a teacher's face or a salesperson's hands
are involved). Compared with broadband UVB treatment, PUVA treatment taken
two to three times a week clears psoriasis more consistently and in fewer
treatments. However, it is associated with more shortterm side effects,
including nausea, headache, fatigue, burning, and itching. Care must be
taken to avoid sunlight after ingesting psoralen to avoid severe sunburns,
and the eyes must be protected for one to two days with UVA-absorbing glasses.
Long-term treatment is associated with an increased risk of squamous-cell
and, possibly, melanoma skin cancers. Simultaneous use of drugs that suppress
the immune system, such as cyclosporine, have little beneficial effect
and increase the risk of cancer.
Light therapy combined with other therapies--Studies
have shown that combining ultraviolet light treatment and a retinoid, like
acitretin, adds to the effectiveness of UV light for psoriasis. For this
reason, if patients are not responding to light therapy, retinoids may
be added. UVB phototherapy, for example, may be combined with retinoids
and other treatments. One combined therapy program, referred to as the
Ingram regime, involves a coal tar bath, UVB phototherapy, and application
of an anthralin-salicylic acid paste that is left on the skin for 6 to
24 hours. A similar regime, the Goeckerman treatment, combines coal tar
ointment with UVB phototherapy. Also, PUVA can be combined with some oral
medications (such as retinoids) to increase its effectiveness.
For more severe forms of psoriasis, doctors sometimes prescribe medicines
that are taken internally by pill or injection. This is called systemic treatment.
Recently, attention has been given to a group of drugs called biologics (for
example, alefacept and etanercept), which are made from proteins produced by
living cells instead of chemicals. They interfere with specific immune system
Methotrexate--Like cyclosporine, methotrexate slows cell
turnover by suppressing the immune system. It can be taken by pill or injection.
Patients taking methotrexate must be closely monitored because it can cause
liver damage and/or decrease the production of oxygen-carrying red blood
cells, infection-fighting white blood cells, and clotenhancing platelets.
As a precaution, doctors do not prescribe the drug for people who have
had liver disease or anemia (an illness characterized by weakness or tiredness
due to a reduction in the number or volume of red blood cells that carry
oxygen to the tissues). It is sometimes combined with PUVA or UVB treatments.
Methotrexate should not be used by pregnant women, or by women who are
planning to get pregnant, because it may cause birth defects.
Retinoids--A retinoid, such as acitretin (Soriatane),
is a compound with vitamin A-like properties that may be prescribed for
severe cases of psoriasis that do not respond to other therapies. Because
this treatment also may cause birth defects, women must protect themselves
from pregnancy beginning 1 month before through 3 years after treatment
with acitretin. Most patients experience a recurrence of psoriasis after
these products are discontinued.
Cyclosporine--Taken orally, cyclosporine acts by suppressing
the immune system to slow the rapid turnover of skin cells. It may provide
quick relief of symptoms, but the improvement stops when treatment is discontinued.
The best candidates for this therapy are those with severe psoriasis who
have not responded to, or cannot tolerate, other systemic therapies. Its
rapid onset of action is helpful in avoiding hospitalization of patients
whose psoriasis is rapidly progressing. Cyclosporine may impair kidney
function or cause high blood pressure (hypertension). Therefore, patients
must be carefully monitored by a doctor. Also, cyclosporine is not recommended
for patients who have a weak immune system or those who have had skin cancers
as a result of PUVA treatments in the past. It should not be given with
6-Thioguanine--This drug is nearly as effective as methotrexate
and cyclosporine. It has fewer side effects, but there is a greater likelihood
of anemia. This drug must also be avoided by pregnant women and by women
who are planning to become pregnant, because it may cause birth defects.
Hydroxyurea (Hydrea)--Compared with methotrexate and
cyclosporine, hydroxyurea is somewhat less effective. It is sometimes combined
with PUVA or UVB treatments. Possible side effects include anemia and a
decrease in white blood cells and platelets. Like methotrexate and retinoids,
hydroxyurea must be avoided by pregnant women or those who are planning
to become pregnant, because it may cause birth defects.
Alefacept (Amevive)--This is the first biologic drug
approved specifically to treat moderate to severe plaque psoriasis. It
is administered by a doctor, who injects the drug once a week for 12 weeks.
The drug is then stopped for a period of time while changes in the skin
are observed and a decision is made regarding the need or further treatment.
Because alefacept suppresses the immune system, the skin often improves,
but there is also an increased risk of infection or other problems, possibly
including cancer. Monitoring by a doctor is required, and a patient's blood
must be tested weekly around the time of each injection to make certain
that T cells and other immune system cells are not overly depressed.
Etanercept (Enbrel)--This drug is an approved treatment
for psoriatic arthritis where the joints swell and become inflamed. Like
alefacept, it is a biologic response modifier, which after injection blocks
interactions between certain cells in the immune system. Etanercept limits
the action of a specific protein that is overproduced in the lubricating
fluid of the joints and surrounding tissues, causing inflammation. Because
this same protein is overproduced in the skin of people with psoriatic
arthritis, patients receiving etanercept also may notice an improvement
in their skin. Individuals should not receive etanercept treatment if they
have an active infection, a history of recurring infections, or an underlying
condition, such as diabetes, that increases their risk of infection. Those
who have psoriasis and certain neurological conditions, such as multiple
sclerosis, cannot be treated with this drug. Added caution is needed for
psoriasis patients who have rheumatoid arthritis; these patients should
follow the advice of a rheumatologist regarding this treatment.
Antibiotics--These medications are not indicated in routine
treatment of psoriasis. However, antibiotics may be employed when an infection,
such as that caused by the bacteria Streptococcus, triggers an outbreak
of psoriasis, as in certain cases of guttate psoriasis.
There are many approaches for treating psoriasis. Combining various topical,
light, and systemic treatments often permits lower doses of each and can result
in increased effectiveness. Therefore, doctors are paying more attention to
Some individuals with moderate to severe psoriasis may benefit from counseling
or participation in a support group to reduce self-consciousness about their
appearance or relieve psychological distress resulting from fear of social
Return to top
Significant progress has been made in understanding the inheritance of psoriasis.
A number of genes involved in psoriasis are already known or suspected. In
a multifactor disease (involving genes, environment, and other factors), variations
in one or more genes may produce a greater likelihood of getting the disease.
Researchers are continuing to study the genetic aspects of psoriasis. Since
discovering that inflammation in psoriasis is triggered by T cells, researchers
have been studying new treatments that quiet immune system reactions in the
skin. Among these are treatments that block the activity of T cells or block
cytokines (proteins that promote inflammation). Several of these drugs are
awaiting approval by the U.S. Food and Drug Administration (FDA).
Advances in laser technology are making it possible for doctors to experiment
with laser light treatment of localized plaques. A UVB laser was recently tested
in a study that was conducted at several medical centers. Although improvements
in the skin were noted, this treatment is not without possible side effects.
In some patients, the skin became inflamed, blistered, or discolored following
Return to top
of Arthritis and Musculoskeletal and Skin Diseases
American Academy of Dermatology
National Psoriasis Foundation
Return to top