Psoriasis is a tricky condition. It’s an autoimmune disease, meaning it happens because your immune system isn’t working the way it should. It sends out messages speeding up skin growth. New cells pile up in patches covered by thick scales.
Other skin conditions -- some of them minor, others more complex -- can also look like psoriasis. Clear skin depends on being able to tell them apart, because each one needs different treatment.
Eczema
Eczema is a group of skin conditions that cause redness, inflammation, and itching. The most common one is called atopic dermatitis, and it’s often what people are talking about when they say “eczema.”
As with psoriasis, experts think eczema comes from faulty genes that affect your immune system, but it’s not an autoimmune disease. The gene can keep your body from making enough filaggrin, a protein that protects the top layer of skin.
Eczema can look like psoriasis because of the redness and dry patches it creates. But it doesn’t have the thick silver scales of psoriasis. Skin is more likely to be dry and leathery. It can get cracks that ooze or bleed.
Eczema often starts in childhood, and some people outgrow it.
Both eczema and psoriasis can range from mild to severe and affect skin anywhere on your body. But eczema is usually inside the elbows and on the backs of the knees. Psoriasis is more common over the knees and elbows.
Seborrheic Dermatitis
Seborrheic dermatitis is another type of eczema. It’s almost always on your scalp and on oily parts of the face where you have sebaceous, or oil-producing, glands. Telltale signs are red areas covered with flaky scales.
The scales are different from those of psoriasis. They’re often white or yellow rather than silvery, and they feel greasy. Psoriasis scales tend to be dry. Seborrheic dermatitis scales also are not as thick or as well-defined as psoriasis plaques. But it can be hard to tell the conditions apart, especially when only the scalp is involved.
Irritant or Allergic Contact Dermatitis
These are two other common kinds of eczema. They cause the same type of itchy, red, inflamed rash as atopic dermatitis. But the cause is an irritant or an allergen that comes in contact with your skin, often your hands or legs.
Poison ivy is the best-known allergen that can cause a reaction. But there are thousands of triggers. They include chemicals, fragrances, and metals. These forms of dermatitis come from the world around you, so if you can avoid your triggers, you can avoid the rash.
In severe cases, skin will blister, ooze, and scab over. But the symptoms go away with time. If you notice any scaling, it will be different from the thick silvery scales of psoriasis.
Parapsoriasis
Parapsoriasis is so similar to psoriasis that it’s even in its name. Think of it as “psoriasis lite.” The patches are more pink than red, and the scales are thinner. There are two forms: small plaque, with patches that are smaller than 2 inches, and large plaque, with patches that are bigger than 2 inches.
You may not notice symptoms or need treatment. But in a very small number of people, parapsoriasis can turn into skin cancer called cutaneous T-cell lymphoma. So your doctor will want to watch you closely.
Skin Cancer
This is the most common type of cancer. It’s most often caused by the sun’s ultraviolet (UV) rays and by tanning beds. Most forms are very treatable, especially when found early.
Some warning signs of skin cancer can mimic psoriasis. It can show up as a scaly pink or red patch. Sometimes, this is the only sign. But as with psoriasis, the area also may be itchy.
If you have psoriasis, it can be hard to tell if a new patch is cancer or the start of another plaque. Your dermatologist can help.
Keratosis Pilaris
When you have keratosis pilaris, hair follicles get clogged with too much of the skin-protecting protein keratin. Bumpy, rough patches are the result. Psoriasis can start as small red bumps, too. But unlike psoriasis, keratosis pilaris isn’t considered a disease. It's more of an annoyance.
It’s not clear why some people get this keratin buildup, but it’s a condition that’s tied to your genes. Young kids get keratosis pilaris most often. It tends to go away in early adulthood, usually around the time psoriasis is gearing up. You’ll also see it in different areas of the body than psoriasis, like the upper arms and the thighs.
Pityriasis Rosea
Pityriasis rosea is a skin problem that can look like psoriasis because it shows up as a scaly rash with a defined shape. Like psoriasis, it can start small, as just one raised patch. It tends to show up in different areas from psoriasis: the stomach, chest, or back. In 1 or 2 weeks, it can spread with more small, scaly areas popping up.
Unlike psoriasis, it’s thought to come from a microbe that first causes a mild respiratory infection. And it usually goes away by itself within a few months. If it’s very itchy, your doctor can suggest treatments.
Ringworm
Ringworm, or tinea, is a rashy infection caused by a fungus. Its name comes from its shape, a raised, red, and often scaly ring.
As with psoriasis, you can get ringworm almost anywhere on your body. It depends on where your skin came into contact with the fungus. It often happens on the trunk, buttocks, and limbs. Unlike psoriasis, the center of the ring is usually clear.
Also unlike psoriasis, ringworm is contagious. Skin-to-skin contact with an infected person is the most likely way to get it. Ringworm can be treated and cured.
Hives
Hives are another type of allergic reaction. The welts often break out when you eat or touch an allergen that causes your skin to swell up. Like psoriasis, hives can be triggered by stress and some types of infections. But many people never find the cause.
You might think of hives as swollen bumps, but they can also be big red patches. That’s why some people confuse hives with psoriasis. Both can be long-term conditions and take an emotional toll.
Treatment is very different. Hives can often be helped by antihistamines, which stop the chemicals that cause the reaction.
Acne
Acne often starts as clogged pores. Breakouts involving blackheads, whiteheads, and pimples usually happen on the face and sometimes the back and chest.
When bacteria mixes with the trapped debris and multiplies, pimples can become red from inflammation. This can be confused with guttate psoriasis, inflamed red spots, usually on the trunk and limbs.
Acne that becomes deep pustules or cysts can look like another form of psoriasis: pustular psoriasis. It’s known for its pus-filled blisters. Unlike acne, pustular psoriasis often happens on the hands and feet and can spread over the entire body. This is a serious medical condition that needs fast attention.
Acne, like psoriasis, can be in your genes. Sometimes, stress can provoke acne, but this is for different reasons than with psoriasis. Stress can boost hormones called androgens, which cause more oil production and more clogged pores.
Rosacea
Rosacea used to be thought of as a type of acne because it causes redness from visible capillaries and pus-filled pimples on the face. Its red patches can be confused with psoriasis (as well as other skin conditions), but the two are unrelated.
One hallmark of rosacea is that it can get worse over time, in some cases thickening the skin of the nose and making it look larger. It’s unclear why some people get rosacea and others don’t. But it tends to run in families.
Psoriasis and rosacea share some triggers, including certain changes in the weather and stress. But rosacea has unique ones, too: hot drinks, spicy food, red wine, and the sun.