It’s easy to confuse eczema and psoriasis, sometimes even for doctors. Both are skin conditions; both can cause itching and patches of red, dry skin; both are chronic; and both tend to be treated in similar ways. Look closely and pay attention, though, and you will start to notice differences.
Both psoriasis and eczema (also known as atopic dermatitis) are thought to be caused, at least in part, by the same thing: an immune system that kicks into overdrive and mistakenly attacks your own body. But the precise process is different for each condition. “It’s different wings of the immune system,” says Emily Newsom, MD, assistant clinical professor of dermatology at UCLA David Geffen School of Medicine.
In psoriasis, overproduction of certain immune-system chemicals causes the outer layer of skin cells to go through the life cycle–forming then sloughing off–in just days rather than a month. The result is a layer of super-fast-forming cells building up on your skin. That’s what causes the thick coating of red, silvery scales on your skin that are characteristic of plaque psoriasis, the most common type of psoriasis.
The outlines of the patches are also different. “Classically, the edges of eczema tend to be more ill-defined, whereas psoriasis is very sharply defined,” says Dr. Newsom.
Symptoms of the two conditions also tend to show up on different parts of the body.
“Eczema is usually on the inside of the arms, backs of knees, and in the folds of your skin,” says Dr. Green. That’s why people with eczema can also get bacterial and yeast infections in those folds where sweat collects.
Psoriasis is more common on the scalp, lower back, knees, and elbows, but it can show up anywhere, including your face. While both conditions are chronic, meaning they never really go away, they can flare up from time to time in response to different triggers.
“Eczema is going to be triggered more by things you’re coming into contact with like fragrance, nickel, pollen, or preservatives,” says Dr. Newsom. For some people, dust, mold, cigarette smoke, wool, polyester, and sometimes hormones can kick off eczema flares.
Psoriasis can be triggered by skin injuries, sunburns, scratches, and infections like strep throat, as well as alcohol and certain medications. Stress and dry weather tend to be triggers for both conditions, says Dr. Newsom. Diet may play a role in both conditions, although more research is needed. Some people with psoriasis find some relief by following an anti-inflammatory diet; people with eczema may benefit from talking to a specialist to help rule out food allergens that could trigger flares.
“Psoriasis is an independent risk factor for heart disease, even controlling for body mass index and weight,” says Dr. Newsom. “The inflammation in the body affects the heart.”
Up to 30% of people with psoriasis will also develop psoriatic arthritis. Some people with eczema go on to develop asthma and hay fever, while a personal or family history of asthma or hay fever can in turn indicate a heightened risk for eczema.
There are effective treatments for both psoriasis and eczema, and those treatments often overlap. For mild forms of either disease, many people get relief from self-care, including moisturizing and avoiding triggers. More severe cases may require medication. Be sure to discuss your symptoms with your dermatologist to help determine the best course of treatment for you.