Who Should Get a Skin Patch Test and What Should You Expect?

If you put 10 people in a room, chances are, one of them has some form of eczema. If that person is you, you probably know that it can be uncomfortable—and very tricky to treat. There’s a lot to unpack about this common skin condition, which isn’t as straightforward as it may seem. 

If you’re dealing with eczema, it may be well worth asking a dermatologist about a skin patch test, which can help determine what—if any—topical ingredients you’re allergic to that may be exacerbating your skin issues. Patch testing can also help you confirm the type of eczema you have, so you’re better positioned to treat it. 

Below, experts tell SELF when it’s a good idea for people with eczema symptoms to get patch-tested, plus pretty much everything else you need to know about the process. 

What is eczema, exactly?

High-level summary: It’s not just one thing. “Eczema is an umbrella term for inflammatory skin conditions,” Kristel Polder, MD, a board-certified dermatologist and adjunct assistant professor at the University of Texas Southwestern Department of Dermatology, tells SELF. According to the American Academy of Dermatology, there are actually seven different types of eczema. While there are differences among them, common symptoms occur across the board: Many people with eczema develop scaly, itchy skin that can be red, purple, brown, or ashy gray in color, depending on your skin tone, Peter Lio, MD, clinical assistant professor of dermatology at the Feinberg School of Medicine at Northwestern University and member of the National Eczema Association’s Scientific & Medical Advisory Council, tells SELF. 

What most people call “eczema”—a rash-like patch of inflamed skin—is usually atopic dermatitis (AD), Dr. Lio says. (This is the most common type of eczema, so it makes sense that the two terms are often used interchangeably.) In terms of what causes AD: “A number of factors contribute to atopic dermatitis. For many people, there’s a genetic component: a deficiency in a protein known as filaggrin, which leads to a compromised, ‘leaky’ skin barrier,” he explains. Plenty of external and environmental factors can also come into play, including weather, diet, and exposure to certain substances and materials, Dr. Lio adds. 

Atopic dermatitis is a chronic condition with no actual cure, but there are multiple ways to manage it and keep it in check, Hayley Goldbach, MD, a board-certified dermatologist and assistant professor of dermatology at Brown University, tells SELF.

Contact dermatitis is another common type of eczema. In this case, the skin reacts to a specific trigger that triggers the inflammation, Dr. Goldbach explains. There’s some additional nuance here, too, as there are two types: allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD).¹ “Allergic contact dermatitis is a type of hypersensitivity to a certain allergen that triggers an immune response and causes inflammation,” says Dr. Goldbach. 

Irritant contact dermatitis, on the other hand, is an injury to the skin—the immune system isn’t involved. As a general rule of thumb, think of irritant contact dermatitis as a bit more universal: If anyone were to overuse retinoids (which tend to cause irritation, especially when you first start using them) or an industrial-strength soap, for example, it’s almost guaranteed that they’ll experience some degree of skin irritation, Dr. Goldbach says. Allergic contact dermatitis is much more individual, because it’s caused by allergens that are unique to each person.¹ (Finding out what those are is where a patch test comes in—more on that in a moment.) 

So, is there a connection between skin allergies and eczema?

A more accurate way of looking at it is by examining the connection between allergic contact dermatitis and atopic dermatitis (again, and please stay with us here, both conditions are types of eczema).