Eczema flare-ups are triggered by a combination of environmental irritants, allergens, stress, weather changes, skin infections, and sometimes foods. Nearly 10% of people aged 16 and older have atopic dermatitis worldwide, and most will cycle through periods of calm skin and frustrating flares. Understanding your personal triggers is the most effective way to reduce how often flares happen and how severe they get.
What Happens in Your Skin During a Flare
Eczema-prone skin has a weaker outer barrier than typical skin. A protein called filaggrin is one of the key building blocks of that barrier, and people with eczema often produce less of it, sometimes due to a genetic mutation. When the barrier is compromised, moisture escapes and irritants get in more easily.
Once something breaches that barrier, skin cells release alarm signals that activate the immune system’s inflammatory response. Immune cells then flood the area and produce inflammatory molecules that cause redness, swelling, and intense itching. Here’s the frustrating part: those same inflammatory molecules further suppress filaggrin production, weakening the barrier even more. This creates a self-reinforcing cycle where inflammation damages the barrier and a damaged barrier invites more inflammation. That’s why flares can escalate quickly once they start and why keeping the barrier intact between flares matters so much.
Irritants in Everyday Products
Chemical irritants are among the most common and avoidable triggers. Soaps, detergents, shampoos, and household cleaners contain surfactants that strip oils from the skin and disrupt its protective layer. Fragrances, whether in skincare products, laundry detergent, or air fresheners, are another frequent culprit. Even products labeled “gentle” or “natural” can contain botanical fragrances that irritate eczema-prone skin.
Formaldehyde, used in textiles since the 1920s to prevent wrinkling, is a known skin sensitizer found across many fabric types. Certain dyes also cause problems. Disperse dyes used to color polyester, acetate, and nylon are now the most common textile dye sensitizers, with disperse blue 124 and disperse orange 3 topping the list. Chrome dyes, used mainly to give wool and silk darker colors, can also trigger reactions.
The Truth About Wool and Fabric
Wool has long been blamed as a universal eczema trigger, but the reality is more nuanced. The itch and prickle you feel from certain fabrics comes down to fiber diameter, not the fiber type itself. Coarse fibers thicker than about 30 to 32 micrometers are stiff enough to poke nerve endings in the skin and trigger itching. This happens with coarse wool, but it also happens with coarse synthetic fibers.
Fine wool with fiber diameters under about 19 to 21 micrometers doesn’t cause that prickle sensation. So a rough acrylic sweater can be worse for your skin than a fine merino wool garment. When choosing clothing, feel the fabric. If it feels scratchy against the inside of your wrist, it will likely irritate eczema-prone areas. Soft cotton, silk, and fine-gauge merino are generally well tolerated.
Indoor and Outdoor Allergens
Allergens provoke a different response than irritants. While irritants damage the skin directly, allergens activate the immune system in people who are sensitized to them.
House dust mites are the most widespread indoor allergen trigger. They thrive in warm, humid environments like bedding, upholstered furniture, and carpeting. The majority of people with eczema are sensitive to dust mites, making bedroom hygiene (hot-washing sheets weekly, using allergen-proof mattress covers) one of the higher-impact changes you can make.
Pet dander is another common trigger. It’s not just the fur but also proteins in animal saliva and skin flakes that can worsen eczema on contact. Mold, both indoor and outdoor, is active primarily in spring and summer, though autumn is peak spore season and a common time for unexpected flares.
Outdoor pollen from trees and grasses tends to cause flares on exposed skin like the face, arms, and legs, particularly during spring and summer. If you notice your eczema worsens seasonally, pollen or mold spores are worth investigating with an allergist.
Weather and Temperature Swings
Both extremes of temperature can trigger flares, though the mechanisms differ. Cold, dry air pulls moisture from exposed skin, accelerating barrier breakdown. Indoor heating during winter compounds this by further lowering humidity. Hot weather triggers flares through a different route: sweating. Sweat contains salts and other compounds that irritate already-compromised skin, and the moisture itself can create an environment that worsens itching.
Research tracking eczema flares across seasons has confirmed that both unusually cold and unusually hot weeks are associated with increased flare activity. The transition periods, when temperatures swing quickly, can be particularly problematic because your skin and clothing choices may be mismatched. Layering and adjusting your moisturizing routine seasonally helps buffer against these shifts.
Bacteria on the Skin
Up to 70% of people with eczema are colonized by Staphylococcus aureus, a type of bacteria that thrives when the skin barrier is weakened. This bacterium is a common cause of flares and secondary skin infections. During a flare, staph populations on the skin tend to spike, producing toxins that ramp up inflammation and further damage the barrier.
Signs that bacteria may be driving a flare include oozing, crusting (especially yellowish crusts), and skin that’s suddenly more painful than itchy. These flares often need different treatment than a standard eczema flare, so they’re worth flagging to a dermatologist early.
Stress and the Skin-Brain Connection
Emotional stress is one of the most commonly reported flare triggers, and the biology behind it is well established. When you’re stressed, your body activates its stress response system, releasing cortisol and other hormones. In the short term, cortisol suppresses inflammation. But chronic or repeated stress disrupts the balance of immune cells in the skin, promotes the release of inflammatory molecules, and directly impairs skin barrier function.
The result is a lower threshold for flares. Irritants or allergens that your skin might normally tolerate can push it over the edge during a stressful period. This also explains why eczema often worsens during major life changes, sleep deprivation, or prolonged anxiety, even when nothing else in your environment has changed.
Food Triggers: Less Common Than You Think
Food is one of the most over-blamed eczema triggers. The foods most consistently linked to eczema flares are cow’s milk, egg, and peanut, with wheat, soy, and fish also implicated in some cases. But true food-triggered eczema is far less common than many people assume, and misidentifying foods as triggers can cause real harm.
Allergy blood tests and skin-prick tests have high false-positive rates for food allergies. Eliminating foods based solely on these results, without confirming through a supervised oral food challenge, is risky. A striking finding from clinical research: 19% of children who eliminated a food they were told to avoid developed new immediate allergic reactions when they ate it again. About 30% of those children experienced anaphylaxis on re-exposure. Eliminating a food can actually promote allergy to it, particularly in young children, because regular oral exposure is one of the ways the immune system learns to tolerate foods.
Unnecessary elimination diets also lead to nutrient deficiencies, poor growth in children, and feeding difficulties. Multiple studies have documented reduced growth velocity as the number of eliminated foods increases. If you suspect a food is triggering your eczema or your child’s, work with an allergist to confirm it through a proper oral food challenge rather than cutting foods on your own.
Keeping Flares at Bay
The single most effective daily habit for preventing flares is consistent moisturizing. Applying a fragrance-free moisturizer immediately after bathing, while the skin is still slightly damp, locks in hydration and reinforces the skin barrier. This “soak and seal” approach reduces the frequency and severity of flares over time. The best moisturizer is one you’ll actually use daily, but thicker creams and ointments generally outperform lotions because they contain more oil and less water.
Beyond moisturizing, flare prevention is largely about identifying and minimizing your personal triggers. Keep a simple log of flares and what preceded them: new products, weather changes, stressful events, foods, or exposure to known allergens. Patterns usually emerge within a few months. Most people with eczema have three or four dominant triggers rather than reacting to everything, and narrowing down your specific list makes management far more targeted and effective.