What Causes Eczema? A Scientific Overview

Eczema might feel like it comes out of nowhere—but under the surface, a lot is happening. It’s a complex condition influenced by genetics, immune responses, and environmental factors.

In this article, we’ll break down what actually causes eczema from a scientific (but easy-to-understand) perspective.

Eczema—also broadly termed dermatitis—refers to a group of inflammatory skin conditions. These are typically marked by intense itching (pruritus), redness (erythema), dryness (xerosis), and often the appearance of small blisters (vesicles), scaling, oozing, or crusting.

Eczema Isn’t Caused by Just One Thing

The exact origin of eczema remains unknown—there’s no single cause. Instead, science points to a complex interaction of several factors, including:

• Genetic predisposition
• Immune system dysregulation
• A weakened skin barrier
• Environmental and lifestyle triggers

The most common form of eczema is atopic dermatitis, and dry skin is a hallmark across nearly all types.

Side Note: Eczema (or dermatitis) involves inflammation of the skin. A compromised skin barrier—one that’s less effective at retaining moisture and defending against irritants—is central to most forms of eczema.

The Genetic Link: Why Eczema Runs in Families

There’s a well-established hereditary link when it comes to eczema. If you or someone in your family has eczema, asthma, or allergic rhinitis (hay fever)—collectively known as the atopic triad—you’re more likely to develop atopic dermatitis.

One major genetic factor? A mutation affecting the gene that produces filaggrin, a protein essential for maintaining the skin barrier.

• Filaggrin deficiency reduces the skin’s ability to retain moisture and defend against irritants.
• This contributes to the dryness and sensitivity often seen in eczema.

But keep in mind: genetics are not destiny. Having a risk-associated gene doesn’t mean you’ll definitely develop eczema.

Side Note: The term “atopy” refers to a genetic tendency to develop allergic conditions like eczema, asthma, and hay fever.

The Skin Barrier Problem

People with eczema have a weakened skin barrier—and that’s a big deal.

This dysfunction leads to:

• Increased water loss through the skin
• Fewer natural moisturizing factors
• Altered skin pH
• Higher permeability to irritants and allergens

This damage is often linked to filaggrin mutations, but it’s also worsened by inflammation and external triggers. A compromised skin barrier doesn’t just make eczema worse—it’s also part of what causes it in the first place.

The Role of the Immune System

In eczema, the immune system becomes overactive and responds to harmless substances as though they’re threats.

This immune imbalance includes:

• Overactivation of T helper cells (Th2, Th1, Th17, Th22)
• Key inflammatory signaling via the JAK-STAT pathway
• Cytokines like IL-4 and IL-13 that drive inflammation
• IL-31 and TSLP, which are major players in eczema-related itching

This immune dysregulation helps explain why eczema tends to flare up again and again, even with treatment.

Environmental and Lifestyle Triggers

Eczema flare-ups are often sparked by external triggers, especially in people who already have a genetic or immune predisposition. Common triggers include:

• Irritants: Soaps, detergents, fragrances, and certain fabrics
• Allergens: Pollen, pet dander, dust mites, and some foods
• Microbes: Especially Staphylococcus aureus (S. aureus)
• Climate factors: Dry air, humidity, heat, and cold
• Stress: Emotional and psychological stress can worsen symptoms
• Frequent exposure to water or chemicals: Often seen in certain occupations, which we explore in “Occupational Dermatitis: Jobs at Risk and Prevention Tips”

Side Note: Eczema is not contagious and has nothing to do with hygiene. These are common myths we break down more in “10 Eczema Myths You Should Stop Believing”.

Why Eczema Starts at Different Ages

Eczema—especially atopic dermatitis—can start at any point in life:

• It often appears in infancy or early childhood
• Some children grow out of it, while others carry it into adulthood
• Others may develop eczema for the first time as adults

These differences likely stem from how genetics and environment interact over time.

If you’re a parent exploring this topic, you might also find “Eczema in Children: What Parents Should Know” and “Who Can Get Eczema? (Age, Gender, Ethnicity Breakdown)” helpful.

Is It Something I Did? (Short Answer: No)

Let’s be clear: eczema is not your fault.

While certain exposures can trigger a flare, the root causes involve genetics, immune function, and skin biology—not something you did or didn’t do.

Side Note: Eczema can look different depending on skin tone. For a visual guide, check out “How Eczema Looks on Different Skin Tones”.

Takeaway: Eczema Is a Puzzle—But You Can Learn to Solve It

Understanding what causes eczema is a powerful first step in managing it. As research advances, treatments become more targeted—and more hopeful.

Ready to Dig Deeper?

Check out “Understanding Trigger Categories: Irritants, Allergens, and More” to learn how to identify and manage your own eczema triggers more effectively.