Psoriasis

Psoriasis: Overview

What is psoriasis?

Psoriasis (sore-EYE-ah-sis) is a chronic (long-lasting) disease. It develops when a person’s immune system sends faulty signals that tell skin cells to grow too quickly. New skin cells form in days rather than weeks.

The body does not shed these excess skin cells. The skin cells pile up on the surface of the skin, causing patches of psoriasis to appear.
Psoriasis may look contagious, but it's not.

You cannot get psoriasis from touching someone who has it. To get psoriasis, a person must inherit the genes that cause it.

Types of psoriasis

If you have psoriasis, you will have one or more of these types:

Some people get more than one type. Sometimes a person gets one type of psoriasis, and then the type of psoriasis changes.


Plaque psoriasis: This type of psoriasis often causes thick patches of skin that are covered with silvery-white scale.

Psoriasis: Signs and symptoms

What you see and feel depends on the type of psoriasis you have. You may have just a few of the signs and symptoms listed below, or you may have many.

Plaque psoriasis

(also called psoriasis vulgaris)

Guttate psoriasis: This type of psoriasis causes small spots that can show up all over the skin.

Guttate psoriasis

Pustular psoriasis

When pus-filled bumps cover the body, the person also may have:

Pustular psoriasis: This type of psoriasis causes pus-filled bumps that usually appear on the foot or hand.

Inverse psoriasis

(also called flexural psoriasis or intertriginous psoriasis)

Inverse psoriasis: This type of psoriasis develops in areas where skin touches skin, such as the armpit.*

Erythrodermic psoriasis

(also called exfoliative psoriasis)

Erythrodermic psoriasis: This type of psoriasis can cause the skin to look like it is badly burned.**

If it looks like a person has erythrodermic psoriasis, get the person to a hospital right away. The person’s life may be in danger.

Top three (3) images used with permission of the American Academy of Dermatology National Library of Dermatologic Teaching Slides.

*Photograph used with permission of the Journal of the American Academy of Dermatology. J Am Acad Dermatol 2004;51:731-8.

**Photograph used with permission of the Journal of the American Academy of Dermatology. J Am Acad Dermatol 2008;58:826-50.


Psoriasis: Who gets and causes

Who gets psoriasis?

People who get psoriasis usually have one or more person in their family who has psoriasis. Not everyone who has a family member with psoriasis will get psoriasis. But psoriasis is common. In the United States, about 7.5 million people have psoriasis. Most people, about 80%, have plaque psoriasis.

Psoriasis can begin at any age. Most people get psoriasis between 15 and 30 years of age. By age 40, most people who will get psoriasis, about 75%, have psoriasis. Another common time for psoriasis to begin is between 50 and 60 years of age.

Whites get psoriasis more often than other races.

Infants and young children are more likely to get inverse psoriasis and guttate psoriasis.

What causes psoriasis?

Scientists are still trying to learn everything that happens inside the body to cause psoriasis. We know that psoriasis is not contagious.

You cannot get psoriasis from swimming in the same pool or having sex.

Scientists have learned that a person’s immune system and genes play important roles. It seems that many genes must interact to cause psoriasis.

Scientists also know that not everyone who inherits the genes for psoriasis will get psoriasis. It seems that a person must inherit the “right” mix of genes. Then the person must be exposed to a trigger.

Many people say that their psoriasis began after they experienced one of these common psoriasis triggers:


Psoriasis: Diagnosis and treatment

How does a dermatologist diagnose psoriasis?

To diagnose psoriasis, a dermatologist:

Sometimes a dermatologist also removes a bit of skin. A dermatologist may call this confirming the diagnosis. By looking at the removed skin under a microscope, one can confirm whether a person has psoriasis.

How do dermatologists treat psoriasis?

Treating psoriasis has benefits. Treatment can reduce signs and symptoms of psoriasis, which usually makes a person feel better. With treatment, some people see their skin completely clear. Treatment can even improve a person's quality of life.

Thanks to ongoing research, there are many treatments for psoriasis. It is important to work with a dermatologist to find treatment that works for you and fits your lifestyle. Every treatment has benefits, drawbacks, and possible side effects.

Outcome

Psoriasis is a chronic (long-lasting) disease of the immune system. It cannot be cured. This means that most people have psoriasis for life. By teaming up with a dermatologist who treats psoriasis, you can find a treatment plan that works for you.

Dermatologists encourage their patients who have psoriasis to take an active role in managing this disease. By taking an active role, you can reduce the effects that psoriasis has on your quality of life.


Psoriasis: Tips for managing

Psoriasis is a long-lasting disease. Here are some things you can do that will help you take control.

Related resources:


A fingertip unit equals the amount of medicine that you can spread on your fingertip, as shown in the photo below.

Psoriasis: Medication

Do you use a psoriasis medicine to treat your skin? If so, the instructions likely tell you how many milligrams of medicine to apply. This can make it difficult to know how much to use.

To help patients figure out how much medicine to apply, dermatologists developed an easy-to-use approach called the “fingertip unit.” All you need to use this approach is your medicine and a clean fingertip. A fingertip unit equals the amount of medicine that you can spread on your fingertip, as shown in the photo below.

Each part of the body requires a specific number of fingertip units. For example, if you have psoriasis on most of your scalp, you need to apply three fingertip units of medicine to your scalp. If psoriasis covers most of your elbow, you’d apply one fingertip unit.

The next time you need to apply psoriasis medicine to your skin, be sure to look at the following table. It shows you how many fingertip units to apply to each part of the body where you have psoriasis.

Area to be treated
No. of fingertip units
Scalp 3
Face and neck 2.5
One hand (front and back) including fingers 1
One entire arm including entire hand 4
Elbow (psoriasis covers most of elbow) 1
Both soles 1.5
One foot (top and bottom) including toes 1.5
One entire leg including entire foot 8
Buttocks 4
Knees (psoriasis covers most of knee) 1
Trunk (from bottom of neck to hipbones) 8
Genitals 0.5

Different parts of the body require a different number of fingertip units.
Chart reproduced from the Psoriasis Guidelines of Care developed by the American Academy of Dermatology. (Menter A, Korman NJ, et al. “Guidelines of care for the management of psoriasis and psoriatic arthritis.” J Am Acad Dermatol 2009;60:643-59.)

References:
Menter A, Korman NJ, et al. “Guidelines of care for the management of psoriasis and psoriatic arthritis.” J Am Acad Dermatol 2009;60:643-59.


© 2019 American Academy of Dermatology. All rights reserved. Reproduction or republication strictly prohibited without prior written permission. Use of these materials is subject to the legal notice and terms of use located at https://www.aad.org/about/legal

You Might Also Enjoy...

What is Mohs surgery?

Used to treat skin cancer, this surgery has a unique benefit. During surgery, the surgeon can see where the cancer stops. This isn’t possible with other types of treatment for skin cancer.

Should I get genetic testing for melanoma?

If you’re worried about getting melanoma, the most-serious skin cancer, you may be wondering whether you should have genetic testing. After all, genetic testing is now used find a person’s risk for many diseases.

Melanoma strikes men harder

Researchers have found yet another way that men and women differ. Melanoma, the most-serious skin cancer, affects the sexes differently.

Your best defense vs. another melanoma

If you’ve been treated for melanoma, you may never get another melanoma. Many people don’t. But it’s important to know that you have a greater risk of getting another one. Anyone who has had melanoma has this risk.

Skin Cancer Prevention

Follow these tips to protect your skin from the damaging effects of sun exposure and reduce your risk of skin cancer ...