Psoriasis is a skin disease that causes red, itchy scaly patches, most commonly on the knees, elbows, trunk and scalp.

Psoriasis is a common, long-term (chronic) disease. It tends to go through cycles, flaring for a few weeks or months, then subsiding for a while or going into remission. Treatments are available to help you manage symptoms. And you can incorporate lifestyle habits and coping strategies to help you live better with psoriasis.

Symptoms

Psoriasis signs and symptoms can vary from person to person. Common signs and symptoms include:

• Red patches of skin covered with thick, silvery scales

• Small scaling spots (commonly seen in children)

• Dry, cracked skin that may bleed or itch

• 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. The most commonly affected areas are the lower back, elbows, knees, legs, soles of the feet, scalp, face and palms.

Most types of psoriasis go through cycles, flaring for a few weeks or months, then subsiding for a time or even going into remission.

There are several types of psoriasis, including:

• Plaque psoriasis. The most common form, plaque psoriasis causes dry, raised, red skin patches (lesions) covered with silvery scales. The plaques might be itchy or tender, and there may be few or many. They usually appear on elbows, knees, lower back and scalp.

• Nail psoriasis. Psoriasis can affect fingernails and toenails, causing pitting, abnormal nail growth and discoloration. Psoriatic nails might loosen and separate from the nail bed (onycholysis). Severe cases may cause the nail to crumble.

• Guttate psoriasis. This type primarily affects young adults and children. It's usually triggered by a bacterial infection such as strep throat. It's marked by small, drop-shaped, scaling lesions on the trunk, arms or legs.

• Inverse psoriasis. This mainly affects the skin folds of the groin, buttocks and breasts. Inverse psoriasis causes smooth patches of red skin that worsen with friction and sweating. Fungal infections may trigger this type of psoriasis.

• Pustular psoriasis. This rare form of psoriasis causes clearly defined pus-filled lesions that occur in widespread patches (generalized pustular psoriasis) or in smaller areas on the palms of the hands or the soles of the feet.

• 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.

• Psoriatic arthritis. Psoriatic arthritis causes swollen, painful joints that are typical of arthritis. Sometimes the joint symptoms are the first or only symptom or sign of psoriasis. And at times only nail changes are seen. Symptoms range from mild to severe, and psoriatic arthritis can affect any joint. It can cause stiffness and progressive joint damage that in the most serious cases may lead to permanent joint damage.

Causes

Psoriasis is thought to be an immune system problem that causes the skin to regenerate at faster than normal rates. In the most common type of psoriasis, known as plaque psoriasis, this rapid turnover of cells results in scales and red patches.

Just what causes the immune system to malfunction isn't entirely clear. Researchers believe both genetics and environmental factors play a role. The condition is not contagious.

Psoriasis triggers

Many people who are predisposed to psoriasis may be free of symptoms for years until the disease is triggered by some environmental factor. Common psoriasis triggers include:

• Infections, such as strep throat or skin infections

• Weather, especially cold, dry conditions

• Injury to the skin, such as a cut or scrape, a bug bite, or a severe sunburn

• Stress

• Smoking and exposure to secondhand smoke

• Heavy alcohol consumption

• Certain medications — including lithium, high blood pressure medications and antimalarial drugs

• Rapid withdrawal of oral or systemic corticosteroids

Causes

Psoriasis is thought to be an immune system problem that causes the skin to regenerate at faster than normal rates. In the most common type of psoriasis, known as plaque psoriasis, this rapid turnover of cells results in scales and red patches.

Just what causes the immune system to malfunction isn't entirely clear. Researchers believe both genetics and environmental factors play a role. The condition is not contagious.

Psoriasis triggers

Many people who are predisposed to psoriasis may be free of symptoms for years until the disease is triggered by some environmental factor. Common psoriasis triggers include:

• Infections, such as strep throat or skin infections

• Weather, especially cold, dry conditions

• Injury to the skin, such as a cut or scrape, a bug bite, or a severe sunburn

• Stress

• Smoking and exposure to secondhand smoke

• Heavy alcohol consumption

• Certain medications — including lithium, high blood pressure medications and antimalarial drugs

• Rapid withdrawal of oral or systemic corticosteroids

Risk factors

Anyone can develop psoriasis. About a third of instances begin in the pediatric years. These factors can increase your risk:

• Family history. The condition runs in families. Having one parent with psoriasis increases your risk of getting the disease, and having two parents with psoriasis increases your risk even more.

• Stress. Because stress can impact your immune system, high stress levels may increase your risk of psoriasis.

• Smoking. Smoking tobacco not only increases your risk of psoriasis but also may increase the severity of the disease. Smoking may also play a role in the initial development of the disease.

Complications

If you have psoriasis, you're at greater risk of developing other conditions, including:

• Psoriatic arthritis, which causes pain, stiffness and swelling in and around the joints

• Eye conditions, such as conjunctivitis, blepharitis and uveitis

• Obesity

• Type 2 diabetes

• High blood pressure

• Cardiovascular disease

• Other autoimmune diseases, such as celiac disease, sclerosis and the inflammatory bowel disease called Crohn's disease

• Mental health conditions, such as low self-esteem and depression

Atopic dermatitis (eczema) is a condition that makes your skin red and itchy. It's common in children but can occur at any age. Atopic dermatitis is long lasting (chronic) and tends to flare periodically. It may be accompanied by asthma or hay fever.

Symptoms

Atopic dermatitis (eczema) signs and symptoms vary widely from person to person and include:

• Dry skin

• Itching, which may be severe, especially at night

• Red to brownish-gray patches, especially on the hands, feet, ankles, wrists, neck, upper chest, eyelids, inside the bend of the elbows and knees, and in infants, the face and scalp

• Small, raised bumps, which may leak fluid and crust over when scratched

• Thickened, cracked, scaly skin

• Raw, sensitive, swollen skin from scratching

Psoriasis and eczema are separate skin conditions, although they share some similar symptoms. Eczema is more commonly found in babies or young children and, unlike psoriasis, may go away over time. It is uncommon to have both eczema and psoriasis at the same time, but it is possible.

How to Tell the Difference Between Eczema and Psoriasis

The most common form of psoriasis generally appears as red, scaly patches of dry skin with an overlying silver scale that may crack and bleed. Eczema patches can be brown-gray or red in appearance, may have pustules, and are typically less well-defined. Eczema tends to form where the skin folds, whereas psoriasis tends to be on the outer parts of the joints. Additionally, while both conditions cause itchy skin, the itching associated with eczema tends to be more extreme and almost universal for people with eczema.

Psoriasis vs. Eczema on the Scalp

While both psoriasis and eczema on the scalp have commonalities such as itching and reddish skin, eczema does not usually appear as dry or with such thick scale. Additionally, eczema scales on the scalp have more of a whitish or yellowish hue versus the silvery one common in psoriasis. 

Psoriasis vs. Eczema on the Face

Psoriasis is typically found on elbows and knees, but a person with scalp psoriasis may find patches extending to the forehead, ears, and other areas close to the face. Eczema may also be found on the face and appears as scaly, dry patches without the silver scale. In both cases, there can be extreme itching and discomfort.

Psoriasis vs. Eczema on the Elbows

Eczema is more often found in folds near the joints, such as the inside or crook of the elbows. On the other hand, psoriasis is commonly found on the elbow itself.

Psoriasis vs. Eczema on the Hands

Due to exposure to soaps, animals, and other allergens, eczema is commonly found on the palms of the hands. Psoriasis on the hands can be found on the back of the hands, palms, knuckles, and nails.

Psoriasis vs. Eczema on the Legs

Psoriasis is often found on knees and legs. The type of psoriasis dictates the size of the spots, from smaller and widespread (guttate psoriasis) to larger plaques (plaque psoriasis). Eczema on the legs tends to form where the skin folds, such as behind the knees, whereas psoriasis is usually on the knee itself.

Psoriasis vs. Eczema: Below the Surface

Although the skin symptoms of psoriasis and eczema can look and feel similar, the conditions are very different below the surface of the skin. Eczema is frequently related to allergies; many people with eczema also have food allergies, seasonal allergies and asthma. Psoriasis is a systemic disease, meaning that it affects the whole body. Psoriasis causes inflammation, fatigue, and other symptoms. About 30 percent of people with psoriasis develop psoriatic arthritis, which can cause progressive joint damage and lead to disability. Psoriatic disease can also cause uveitis (eye inflammation), which can result in loss of vision.

Causes of Psoriasis vs. Eczema

Eczema and psoriasis are caused by overactivation of different inflammatory pathways within the immune system. The cause of psoriasis, while not completely understood, is an autoimmune reaction wherein the immune system responds to a trigger and recruits many inflammatory cells into the skin.

The cause of eczema is not clear, but it is thought to be an extreme sensitivity — sometimes caused by an allergy — to certain triggering substances. It may also be due to a defect in the proteins that form the barrier of the skin. Common triggers for eczema flare-ups include animals, fabrics, soaps, metals, and certain medications. In other words, psoriasis is caused when your immune system attacks itself, and eczema is caused when your immune system overreacts to an outside substance.

Diagnosis of Psoriasis vs. Eczema

Psoriasis is usually diagnosed when a dermatologist performs a visual exam and takes your medical and family history. In some cases, the doctor may do a biopsy (remove a small piece of skin for laboratory testing) to confirm the diagnosis. Read more details about psoriasis diagnosis.

Similarly, eczema is typically diagnosed by observing the skin and asking questions about medical and family history. A biopsy may also be done to help diagnose eczema. A patch test (attaching samples of different substances to the skin with tape) may be performed to see if the itchy rash is caused by an allergy to an external contact.

In some cases, genetic testing may be needed to differentiate between psoriasis and eczema.

Acne vulgaris is a common chronic skin disease involving blockage and/or inflammation of pilosebaceous units (hair follicles and their accompanying sebaceous gland). Acne can present as noninflammatory lesions, inflammatory lesions, or a mixture of both, affecting mostly the face but also the back and chest.

A skin condition that occurs when hair follicles plug with oil and dead skin cells.

Acne is most common in teenagers and young adults.

Symptoms range from uninflamed blackheads to pus-filled pimples or large, red and tender bumps.

Vitiligo is a condition in which the skin loses its pigment cells (melanocytes). This can result in discoloured patches in different areas of the body, including the skin, hair and mucous membranes. Vitiligo (vit-ih-LIE-go) is a disease that causes loss of skin colour in patches.

Vitiligo occurs when pigment-producing cells die or stop functioning.

Loss of skin colour can affect any part of the body, including the mouth, hair and eyes. It may be more noticeable in people with darker skin.

Infection with the herpes simplex virus around the border of the lips.

Oral herpes spreads through close personal contact, such as kissing.

Oral herpes causes tiny, fluid-filled lesions called cold sores or fever blisters, which can recur.

Medication can speed up healing and reduce recurrence.

Cold sores — also called fever blisters — are a common viral infection. They are tiny, fluid-filled blisters on and around your lips. These blisters are often grouped together in patches. After the blisters break, a scab forms that can last several days. Cold sores usually heal in two to three weeks without leaving a scar.

Cold sores spread from person to person by close contact, such as kissing. They're usually caused by herpes simplex virus type 1 (HSV-1), and less commonly herpes simplex virus type 2 (HSV-2). Both of these viruses can affect your mouth or genitals and can be spread by oral sex. Cold sores are contagious even if you don't see the sores.

Dry skin makes the skin look and feel rough, itchy, flaky or scaly. The location where these dry patches form vary from person to person. It's a common condition that affects people of all ages.

Dry skin, also known as xerosis or xeroderma, has many causes, including cold or dry weather, sun damage, harsh soaps, and overbathing.

You can do a lot on your own to improve dry skin, including moisturizing and practicing sun protection year-round.

A skin rash caused by contact with a certain substance.

The substance might irritate the skin or trigger an allergic reaction. Some common culprits include soap, cosmetics, fragrances, jewellery and poison ivy.

The main symptom is a red rash wherever the skin came into contact with the irritant.

Avoiding the irritant or allergen should allow the rash to clear in two to four weeks. Creams or medication can help reduce itching and other symptoms.

A condition in which brown patches appear on the face.

Melasma can be due to hormonal changes during pregnancy or from sun exposure. Women are much more likely than men to develop this condition.

The brown or grey-brown patches of melasma appear most often on the cheeks, forehead, nose and chin.

In women, melasma often fades on its own after pregnancy or after an affected woman stops taking contraceptive pills. Skin lightening creams can help lasting melasma.

A small, fleshy bump on the skin or mucous membrane caused by human papillomavirus.

Warts are caused by various strains of human papillomaviruses. Different strains may cause warts in different parts of the body. Warts can be spread from one location on the body to another or from person to person by contact with the wart.

The main symptom is a fleshy, painless growth on the skin. Common areas affected include the hands, feet and genitals.

A rough, scaly patch on the skin caused by years of sun exposure.

Actinic keratoses usually affects older adults. Reducing sun exposure can help reduce risk.

It is most common on the face, lips, ears, back of hands, forearms, scalp and neck. The rough, scaly skin patch enlarges slowly and usually causes no other signs or symptoms. A lesion may take years to develop.

Molluscum contagiosum is an infection caused by a poxvirus (molluscum contagiosum virus). The result of the infection is usually a benign, mild skin disease characterized by lesions (growths) that may appear anywhere on the body.

A viral skin infection that results in round, firm, painless bumps.

The condition spreads through contact with an infected person or a contaminated object.

Though painless, the small bumps might itch. Scratched bumps can spread infection to surrounding skin.