What Causes Eczema? Understanding Triggers and Risk Factors

If you're living with eczema (atopic dermatitis), understanding what causes your symptoms is the first step toward better management. Eczema affects approximately 10-20% of children and 2-10% of adults worldwide—that's more than 200 million people globally dealing with itchy, inflamed skin. While there's no simple answer to what causes eczema, research shows it results from a complex interaction between your genes, immune system, skin barrier function, and environmental factors.

This guide explores both the root causes that make you susceptible to eczema and the triggers that activate flare-ups, helping you identify your personal patterns and work toward clearer, more comfortable skin.

Causes vs. Triggers: What's the Difference?

Before diving into specifics, it's important to understand the distinction between causes and triggers. The underlying causes of eczema are the fundamental factors that make you susceptible to developing the condition in the first place. These include genetic mutations, immune system characteristics, and skin barrier defects that you're born with or develop early in life.

Triggers, on the other hand, are environmental or external factors that don't cause eczema but activate flare-ups in people who already have the condition. A trigger might make your eczema worse or bring on symptoms in skin that was previously clear, but it won't cause eczema in someone without the underlying susceptibility.

Root Causes of Eczema

Genetic Factors

Genetics plays a major role in eczema development. Research shows that approximately 75% of eczema risk comes from inherited genetic factors. The most well-studied genetic link involves mutations in the filaggrin gene (FLG), which provides instructions for making a protein crucial to your skin's protective barrier.

About 20-30% of people with eczema have these filaggrin mutations, compared to only 8-10% of people without the condition. When filaggrin doesn't work properly, your skin can't retain moisture effectively and becomes more vulnerable to irritants, allergens, and bacteria slipping through.

Beyond filaggrin, scientists have identified 58 genetic locations associated with eczema susceptibility. These genes affect various aspects of skin function and immune response, including proteins involved in immune signaling, inflammation control, and the structural integrity of your skin's outer layers.

Skin Barrier Dysfunction

Your skin's outer layer, the stratum corneum, acts like a brick wall—skin cells are the bricks, and lipids (fats) are the mortar holding everything together. In healthy skin, this barrier keeps moisture in and harmful substances out. People with eczema have a compromised barrier that's more like a wall with gaps.

This barrier dysfunction occurs for several reasons. Beyond filaggrin mutations, people with eczema often have reduced levels of ceramides and other essential lipids that help seal the spaces between skin cells. Without adequate ceramides, water evaporates more easily, leading to the characteristic dryness of eczema. At the same time, this leaky barrier allows bacteria, allergens, and irritants to penetrate deeper into the skin.

Research shows that barrier dysfunction isn't just a symptom of eczema—it's actually one of the primary causes. Even in areas of skin that look normal, people with eczema have measurably increased water loss through their skin compared to people without the condition.

Immune System Dysregulation

Eczema involves an overactive immune response. Your immune system acts like it's constantly on high alert, overreacting to substances that wouldn't bother most people. This immune dysfunction involves multiple pathways, including specific types of white blood cells called T-cells and various signaling proteins.

When your immune system detects something it perceives as a threat through the weakened skin barrier, it releases inflammatory signals that cause redness, swelling, and itching. This creates a vicious cycle: scratching damages the barrier further, allowing more irritants in, which triggers more inflammation.

Interestingly, research has also found that bacteria on the skin's surface, particularly Staphylococcus aureus, not only infects eczema-affected skin but may actually contribute to causing flares by triggering immune responses that increase inflammation.

Risk Factors for Developing Eczema

Family History

Having family members with eczema dramatically increases your risk. Studies show that if one parent has eczema, there's about a 60% chance their child will develop it. When both parents have eczema, that risk jumps to nearly 80%. About 70% of people with eczema have a positive family history of allergic conditions.

The connection extends beyond eczema alone. Family history of asthma or hay fever increases your risk of developing eczema by 2-3 times. This cluster of conditions—eczema, asthma, and allergic rhinitis—is called the "atopic triad" and tends to run in families together.

Age

Eczema most commonly begins in early childhood. About 60% of people with eczema develop symptoms before their first birthday, and 90% experience their first symptoms before age five. While many children outgrow eczema as they get older, some continue to have symptoms into adulthood, and in rare cases, eczema can first appear in adults who never had it as children.

Other Allergic Conditions

If you have asthma, hay fever, or food allergies, you're at higher risk for developing eczema. Up to 30% of people with eczema also have food allergies. This connection reflects the shared immune system dysfunction underlying these allergic conditions.

Gender and Ethnicity

Females are slightly more likely to develop eczema than males, with global prevalence rates of 2.8% in females compared to 2.4% in males. Recent genetic research has also revealed that eczema affects different ethnic groups differently, with certain genetic variants being more common in specific populations.

Common Environmental Triggers

While the factors above determine who develops eczema, triggers are what cause day-to-day flare-ups. Understanding your specific triggers is crucial for managing symptoms effectively.

Weather and Climate

Temperature and humidity changes are among the most common eczema triggers:

• Cold, dry winter air: Low humidity and indoor heating strip moisture from your skin, making it dry and cracked. Cold winds can further irritate already sensitive skin.

• Hot, humid weather: While moisture can help some people, heat and sweating trigger flares in many others. Sweat is slightly acidic and salty, which can irritate inflamed skin.

• Rapid temperature changes: Moving between heated indoor spaces and cold outdoor air, or between air-conditioned rooms and summer heat, can shock your skin and trigger symptoms.

Maintaining indoor humidity levels between 45-60% and using a humidifier in dry conditions can help minimize weather-related flares.

Irritants in Products and Materials

Many everyday products contain ingredients that irritate sensitive skin:

• Fragrances: Whether synthetic or natural, fragrances are one of the biggest culprits in triggering eczema flares. They're found in soaps, lotions, laundry detergents, fabric softeners, and cleaning products.

• Harsh soaps and detergents: Products with strong surfactants strip away your skin's natural oils, further compromising the barrier. Bubble baths are particularly problematic.

• Fabric softeners and dryer sheets: These products coat fabrics with synthetic fragrances and chemicals that can remain in contact with your skin all day.

• Preservatives and dyes: Found in many personal care and laundry products, these additives can trigger reactions in sensitive individuals.

Look for products labeled "fragrance-free" and "dye-free." Note that "unscented" products may still contain masking fragrances, so fragrance-free is the better choice.

Clothing and Fabrics

What you wear matters when you have eczema:

• Wool: The rough texture causes mechanical irritation and should be avoided completely, especially next to skin.

• Synthetic fabrics: Polyester, nylon, and spandex can trap heat and moisture, potentially worsening symptoms.

• Best choices: Soft, breathable natural fabrics like cotton, bamboo, and silk are generally well-tolerated. Choose loose-fitting clothing to minimize friction.

Allergens

Environmental and food allergens can trigger eczema flares in sensitized individuals:

Airborne allergens:

• Dust mites: These microscopic creatures live in bedding, carpets, and upholstered furniture. Their droppings are a major allergen for many people with eczema.

• Pet dander: Skin cells, saliva, and proteins from cats, dogs, and other animals can trigger reactions.

• Pollen: Tree, grass, and weed pollens can trigger flares, particularly in people with head and neck eczema.

• Mold: Both indoor and outdoor mold spores can act as triggers.

Food allergens:

Up to 30% of people with eczema have food allergies. The most common culprits include cow's milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish. Food reactions can be immediate or delayed up to 48 hours, making them tricky to identify. It's important to note that food can worsen eczema symptoms but is rarely the root cause of the disease itself.

Stress and Emotional Factors

Stress is one of the most frequently reported eczema triggers, affecting up to 35% of people with the condition. When you're stressed, your body releases stress hormones that can increase inflammation throughout your body, including in your skin. Stress can also disrupt sleep, weaken your immune system, and lead to increased scratching—all of which worsen eczema.

The relationship between stress and eczema is bidirectional: stress triggers flares, and dealing with uncomfortable, visible skin symptoms creates more stress. Breaking this cycle through stress management techniques like meditation, exercise, or therapy can improve symptoms.

Sweating and Exercise

In one study, 96% of people with eczema reported that sweating made their condition worse. Sweat contains salt and other substances that can irritate already inflamed skin. Heat itself is also a trigger—as your body temperature rises during exercise, blood flow to the skin increases, which can intensify itching.

This doesn't mean you should avoid exercise, which has many benefits including stress reduction. Instead, choose lower-intensity activities when possible, exercise in temperature-controlled environments, wear breathable cotton clothing, keep a towel handy to blot sweat, and shower promptly after working out.

How to Identify Your Personal Triggers

Triggers vary significantly from person to person. What causes severe flares in one person might not affect another at all. Identifying your specific triggers takes detective work, but it's one of the most effective ways to manage eczema.

Keep a Symptom Diary

Track your daily activities, diet, products used, weather conditions, stress levels, and skin symptoms. After several weeks, patterns often emerge. Document:

• Date and time of flares

• Severity of symptoms (rate 1-10)

• Location of affected areas

• Foods consumed (with timing)

• New products or clothing worn

• Weather conditions and temperature

• Stress events or emotional state

• Physical activity and sweating

• Sleep quality

Remember that reactions can be delayed, sometimes appearing 24-48 hours after exposure. This delay makes trigger identification challenging but also highlights why consistent tracking is important.

Elimination Testing

If you suspect a specific product or food is triggering flares, try eliminating it completely for 4-6 weeks to see if symptoms improve. Then reintroduce it to see if symptoms return. This approach works best when you test one thing at a time.

Important: If you're considering eliminating major food groups, especially for a child, consult with a healthcare provider or registered dietitian first. Unnecessary food restrictions can lead to nutritional deficiencies and may complicate true food allergy diagnosis.

Professional Allergy Testing

If your diary suggests specific allergens might be triggers, your doctor can perform tests to identify sensitivities:

• Skin prick tests: Small amounts of common allergens are applied to your skin to check for reactions

• Blood tests: Measure antibodies to specific allergens

• Patch tests: Used to identify contact allergens that cause delayed reactions

These tests aren't perfect—positive results don't always mean that allergen triggers your eczema, and negative results don't rule out sensitivity. Your symptom diary provides crucial context that helps doctors interpret test results accurately.

When to See a Dermatologist

You should consult a dermatologist if:

• Your symptoms are severe, widespread, or interfering with daily activities and sleep

• Over-the-counter treatments aren't providing adequate relief

• Your skin shows signs of infection (increased redness, warmth, oozing, yellow crusting, or fever)

• You're struggling to identify your triggers despite keeping a symptom diary

• You suspect food allergies might be involved

• Your child has eczema, especially if it's moderate to severe

A dermatologist can confirm your diagnosis, prescribe stronger treatments if needed, perform or arrange allergy testing, and help you develop a comprehensive management plan tailored to your specific situation. Early intervention is particularly important for children, as proper management can reduce symptom severity and may lower the risk of developing other allergic conditions.

Key Takeaways

Eczema develops from a combination of genetic susceptibility, skin barrier dysfunction, and immune system irregularities. These underlying causes make you vulnerable to the condition, while environmental triggers activate flare-ups in day-to-day life.

While you can't change your genes, understanding your specific triggers empowers you to make informed choices about products, clothing, activities, and environmental factors that affect your skin. By identifying and avoiding your personal triggers, managing stress, maintaining a consistent skincare routine with barrier-repairing moisturizers, and working with healthcare providers when needed, you can significantly reduce flare frequency and severity.

Remember that eczema is a chronic condition requiring ongoing management rather than a one-time cure. What works for someone else might not work for you, and your triggers may change over time. Be patient with yourself as you learn what your skin needs, and don't hesitate to seek professional guidance when you need additional support.