Your skin is the largest organ in (or on) your entire body—and because it's essentially that body's protective outside layer, there are a number of conditions that can affect it (think: psoriasis, hives, acne, rosacea—any kind of irritation or inflammation of the skin).
Two more of those skin conditions are atopic dermatitis and eczema, and while the two terms are commonly used interchangeably, they're not necessarily the same thing. Here, dermatologist help to break down how atopic dermatitis and eczema differ—and what other conditions might present similarly.
What is atopic dermatitis—and how is it different than eczema?
Atopic dermatitis is a common, chronic, inflammatory skin condition. "It's a genetic condition in which people's skin has a higher propensity to get compromised, and they get inflammation from irritants that are in our environment more easily," David Kim, MD, a board-certified cosmetic dermatologist, tells Health. Basically, people with atopic dermatitis have skin that struggles to keep irritants out, and it's extra sensitive to said irritants. The result: patches of discolored, itchy, scaly skin.
People with atopic dermatitis can experience common symptoms (dry, itchy skin and red rashes) anywhere on the body, but the most common sites are on the arms, elbows, and behind the knees, Dendy Engleman, MD, FAAD, a board-certified dermatologist, tells Health. (Other spots include the hands, face, and scalp.)
Many dermatologists refer to atopic dermatitis as eczema. However, atopic dermatitis is technically just one specific form of eczema. Eczema (dermatitis, or inflammation of the skin) is essentially an umbrella term for different types of skin swelling and irritation, according to the US National Library of Medicine (MedlinePlus); atopic dermatitis falls under that umbrella.
So why the interchangeable terms? "There are many different types of eczema, but [atopic dermatitis] is the most common type that we see," Tiffany Jow Libby, MD, director of Mohs micrographic and dermatologic surgery at Brown Dermatology in Rhode Island, tells Health. It affects an estimated one in 10 Americans, per the American Academy of Dermatology (AAD), including adults and children.
RELATED: 12 Atopic Dermatitis Treatments Dermatologists Rely On to Manage the Chronic Skin Condition
What are the other types of eczema or dermatitis?
As mentioned, there are a few other types of eczema out there. Every form of eczema shares one main symptom: intense itching. However, that itching can be caused by different things, or manifests on the skin in different ways. Here's an overview of the other six types of eczema (there are seven overall), and what you need to know about each.
This type of eczema shows up as an itchy rash that flares up almost immediately after someone touches or comes into contact with an irritant or allergen (known as irritant contact dermatitis and allergen contact dermatitis, respectively), per the AAD. It's most commonly seen on the hands, but can also pop up on the eyelids, armpits, or other parts of the body.
While it shares symptoms with traditional eczema, Dr. Kim says that contact dermatitis flares up quickly—usually within 48 hours of contact—while atopic dermatitis develops more slowly. Once the allergen or trigger is removed (and a person is treated with topical steroids), the contact dermatitis usually goes away
Dyshidrotic eczema is another common form of eczema, which manifests as small, extremely itchy blisters on the hands and feet, according to the National Eczema Association (NEA). It's most common in younger adults—usually people ages 20–40—and it's found more frequently in women.
Like atopic dermatitis, dyshidrotic eczema is often a chronic condition, which means people can have periods of active symptoms (flare-ups) and periods of no symptoms. Though the condition itself doesn't have a known cause, certain situations can trigger flares, like extensive exposure to water (think: excessive hand-washing or sweating), says Dr. Engleman. Metals like nickel, and extremely stressful situations can also trigger flare-ups.
According to the NEA, symptoms of dyshidrotic eczema can improve through a course of topical steroids, combined with soaking or applying cool compresses to affected areas, but if symptoms persist other treatments like light therapy or oral steroids may be used.
RELATED: How to Identify Atopic Dermatitis on the Face—And What to Do About It
This type of eczema creates coin-shaped patches of irritated, itchy skin, says Dr Engelman (the word "nummular" actually comes from the Latin word for "coin," per the NEA). Nummular eczema can pop up at any age, but it's more common in men than women.
Like other types of eczema, there isn't a clear cause of nummular eczema—it's a chronic condition that can flare-up due to certain triggers like very dry or sensitive skin, or even trauma to the skin like insect bites, scrapes, or burns.
Though nummular eczema can look like a few other skin conditions (the NEA lists psoriasis, ringworm, fungal infections, or other types of eczema), once a diagnosis is made, it can go away "completely" with the right treatment, which can include a topical steroid used in conjunction with a topical antibiotic.
Neurodermatitis—a type of eczema that affects about 12% of the population, per the NEA—is actually a result of intensely itching a specific patch (or patches) of the skin. Here's the catch: The more you scratch, the itchier it becomes, the AAD says. The intense, repeated scratching can also make the patches of skin become dry, leathery, and thickened—a process called lichenification, per the NEA. This type of eczema can occur anywhere you're already scratching, but it most commonly shows up on the feet, ankles, hands, wrists, elbows, shoulders, neck and scalp.
Treatment for neurodermatitis focuses on two things, per the NEA: healing the skin and ending the itching-scratching cycle. That means, in addition to topical treatments (steroids, ointments, or even coverings for affected areas), patients also benefit from counseling or cognitive behavioral therapy (CBT) to stop their scratching urges.
RELATED: Atopic Dermatitis Can Commonly Affect the Hands—Here's What to Watch Out For
This one's tricky: While many consider seborrheic dermatitis (aka, dandruff) a chronic form of eczema, some dermatologists are hesitant to label it as such. Technically speaking, seborrheic dermatitis appears on the body where there are an abundance of oil-producing glands (sebaceous glands), like the upper back, nose, and scalp, per the NEA. It can cause itching, redness, and scaling where it shows up—which sounds a lot like how other forms of eczema present.
But here's where it gets different: Seborrheic dermatitis is actually an inflammatory reaction to certain yeasts or fungi (Malassezia, specifically) that normally lives on the skin's surface. Typically, it doesn't cause issues, but when there's an overgrowth of it, your immune system can react negatively, says Dr. Kim.
The treatment is different for seborrheic dermatitis is different than for other types of eczema too: While most types of eczema are treated with steroids or anti-inflammatory topicals, dermatologists often prescribe anti-fungal shampoos to fight seborrheic dermatitis, says Dr. Kim.
This type of eczema is typically seen in people over the age of 50, per the NEA—that's because if most frequently affects people with poor circulation. Stasis dermatitis shows up mainly on the feet or lower legs, but can (uncommonly) show up on other parts of the body, too.
This type of eczema shows up alongside ankle swelling as orange-brown speckles of discoloration (sometimes called cayenne pepper spots), per the NEA. Other symptoms, like other forms of eczema, include: itching, dryness, or redness.
Treatment of stasis dermatitis depends on identifying the underlying cause—poor circulation, high blood pressure, multiple pregnancies, and heart or kidney failure, to name a few—and treating that, as well as the symptoms.
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