More than eight million people in the United States have psoriasis, which most commonly causes itchy, scaly patches of thick, red, dry skin called plaques. While there are signs and symptoms that set the disease apart from other conditions affecting the skin, it isn’t always easy to distinguish it at first.
Because psoriasis can look like other skin conditions that cause scaly patches and itchy rashes with inflammation, it is often confused with various disorders. These may include common skin conditions, such as acne, eczema, or heat rash. Psoriasis can also resemble and be confused with the fungal infection known as ringworm.
There are five types of psoriasis — plaque psoriasis, guttate psoriasis, pustular psoriasis, inverse psoriasis, and erythrodermic psoriasis — none of which is contagious. Each type of psoriasis causes a different skin rash and can appear on different areas of the body.
Most of the time, psoriasis can be diagnosed with a physical examination. A skin biopsy may be needed to rule out other possibilities and arrive at a definitive diagnosis.
When trying to identify psoriasis, here are some things you can look out for.
(The images that follow are of real people with medical conditions and are graphic.)
Is That Rash Psoriasis, or Is It Something Else?
Dermatologist Andrew Alexis, MD, walks through some ways to identify psoriasis and differentiate it from other skin conditions.
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Plaque Psoriasis: Red Bumps and Silvery Scales
Plaque psoriasis is the most common form of the chronic skin condition, affecting about 80 percent of people with psoriasis. Plaque psoriasis usually starts as small red bumps on the skin. On lighter skin, it then develops into red patches with a silvery, scaly coating — these raised patches are called plaques. On darker toned skin, the plaques may look dark brown, or purple with grayish scale, and plaques may be thicker with more scaling.
Psoriasis plaques can consist of a few spots of dandruff-like scales or major eruptions that cover large areas. Plaques usually show up on elbows, knees, and the lower back, and they can last for a couple of weeks to a few months.
Guttate Psoriasis: Small Red Spots
The rash caused by guttate psoriasis is characterized by multiple small, round red spots on the skin, usually widespread across the trunk and limbs. Often resulting from a bacterial or viral infection in children, such as strep throat, these spots come on suddenly and sometimes require oral medication or injections. Mild cases can be treated with topical medications.
Pustular Psoriasis: Pus-Filled Bumps
Pustular psoriasis is a rare form of psoriasis characterized by pus-filled bumps (called pustules) surrounded by inflamed, discolored skin. These blisters are not infectious or contagious, but they may cause soreness and pain.
Factors that may increase your risk of pustular psoriasis include use of systemic steroid medication, hydroxychloroquine, or certain antibiotics, overexposure to UV light, stress, pregnancy, and infection.
Occasionally, the pustules can cover the entire body, which is known as generalized pustular psoriasis, or von Zumbusch psoriasis, a serious condition that requires immediate medical attention.
Inverse Psoriasis: Smooth, Shiny Lesions
Inverse psoriasis forms smooth, shiny lesions in body folds, where skin meets skin — such as the underarms, behind the knees, under the breasts, or around the groin. On skin of color the lesions may be purplish, brown, or darker than the surrounding skin, while they tend to be red on white skin.
This condition can cause sore skin, which may worsen if you sweat or rub the affected area.
Erythrodermic Psoriasis
This rare form of psoriasis may appear as discoloration on more than 75 percent of the body. You may notice shedding or peeling. On darker skin tones, erythrodermic psoriasis may look purple or brown instead of red. Itching, swelling, shedding, hair loss, nail changes, fever, chills, fatigue, dehydration, and increased heart rate may also occur.
Contact your doctor immediately for treatment if these symptoms occur.
Seborrheic Dermatitis: Itchy, Scaly Plaques
The common skin rash seborrheic dermatitis (scalp eczema) also causes scaly, itchy skin patches. It can occur on your scalp, where it may be called dandruff (and may resemble scalp psoriasis), or on your face and chest. While doctors don’t know the exact cause, it occurs across the age spectrum, in babies as well as in adults, and is usually treated with medicated shampoos or creams and lotions.
Pityriasis Rosea: A Raised, Red Rash in a Christmas Tree Shape
Pityriasis rosea often begins as an oval, slightly raised scaly spot on the face, chest, abdomen or back. This is what’s known as a herald patch and may be up to 4 inches across. Smaller red spots may follow, around the middle of the body in a shape that looks like a pine tree.
The rash can be itchy. It tends to clear up on its own within 10 weeks. The exact cause isn’t known, but it may be triggered by a viral or bacterial infection or a reaction to a medication.
Eczema: Red, Itchy, Irritated Skin
Like psoriasis, eczema is a chronic skin condition that often causes intense itching. Scratching causes redness and inflammation of the skin, leading to a worsening of the eczema. Red, dry patches of skin can occur in multiple parts of the body and people with darker skin tones may see darkening or lightening of the skin in inflamed areas. Scratching can also cause a secondary bacterial infection. The most common type of eczema, atopic dermatitis, is caused by a combination of genetic, environmental, and immune-related factors.
Your doctor may prescribe a steroid cream or other medications if eczema is severe. Keeping your skin hydrated and moisturized is also an important part of managing eczema.
Acne: Blocked Pores That Lead to Pimples
Pustular psoriasis, which forms white blisters that are filled with pus and surrounded by red skin, may be confused with pimples. Far more common than psoriasis, acne also causes a pus-filled pimple eruption. However — unlike psoriasis — acne develops when pores become clogged with excess oil, dead skin cells, and bacteria. Acne, thought to be hormonally related, is common in teens and young adults and occurs on the face, neck, back, or chest. Pustular psoriasis is usually seen in adults and often occurs on the palms of the hands or soles of the feet (palmopustular psoriasis), not commonly on the face.
Acne treatment typically involves a combination of topical medications and, if stubborn, systemic oral drugs.
Measles: A Facial Rash That Can Cover the Body
Measles is an upper respiratory infection accompanied by fever, cough, runny nose, and a skin rash of small, red spots. The rash can look like guttate psoriasis, however, the measles skin rash usually starts on the face and spreads down to cover the body. Measles rash is also flat, while the rash of psoriasis is typically raised. Measles is caused by a virus and is highly contagious; declining vaccination rates have made it more common in the United States.
Ringworm: Fungal Infections of the Skin
Tinea is a type of fungal infection that resembles some symptoms of psoriasis. Psoriasis can cause the thick fingernails symptomatic of fungal nail infections, and both can cause red, itchy skin rashes. When tinea grows on your skin, it can cause a circular, scaly, red skin rash that clears in the middle, called ringworm. Fungal infections of the nails can be hard to treat and may require taking a prescription antifungal medication, but infections of the skin usually go away when an antifungal ointment or cream is applied for 2 to 4 weeks.
Heat Rash: Sweating That Leads to Bumpy, Red Skin
Inverse psoriasis, which forms in the armpits and skin folds under breasts or in groin areas, making the skin red and shiny, is made worse by sweating. It can resemble heat rash, which also makes your skin red and forms in skin folds of the groin, breasts, and armpits. Heat rash occurs in hot, humid conditions. Sweating can cause your pores to get blocked and results in a bumpy, red skin rash that can feel prickly. Heat rash is more common in infants but can also affect older children and adults.
Dry, Cracked Skin: Irritation That Can Lead to Infection
Dry, cracked skin is a psoriasis symptom. But dry air can also cause your skin to become dry and itchy. When the skin is dry and irritated, it’s more likely to get infected. Infection may cause your skin to become red and swollen. If you have any skin rashes that keep coming back or won’t go away, see your doctor. Most cases of psoriasis can be diagnosed with a physical examination; but because psoriasis can look like many other skin conditions, a skin biopsy may have to be done to definitively diagnose it.
The Takeaway
- Psoriasis is a challenging skin condition affecting more than eight million people in the United States, often appearing as scaly, itchy patches and it may resemble other skin conditions, complicating diagnosis and treatment.
- Given that psoriasis can be mistaken for eczema, acne, or even heat rash, a proper diagnosis from a healthcare professional may include a physical exam and, sometimes, a skin biopsy for more certainty.
- Recognizing psoriasis and distinguishing it from infections such as measles, which requires immediate medical attention, is important; if you suspect a viral or bacterial cause for your skin changes, consult a healthcare provider promptly.
- Consider maintaining a detailed record of your skin symptoms and any potential triggers or relevant family medical history as it may assist your healthcare provider in formulating an effective treatment plan.