Eczema flares happen when something disrupts your skin’s protective barrier or triggers an overreaction from your immune system. The list of culprits is long, ranging from the soap you use to the stress you carry to the bacteria already living on your skin. Understanding which triggers affect you personally is the key to reducing flare frequency, because eczema rarely has a single cause.
Why Eczema-Prone Skin Is Vulnerable
Healthy skin works like a brick wall: tough protein cells (the bricks) held together by a fatty lipid layer (the mortar). In eczema-prone skin, this wall has gaps. Many people with eczema carry mutations in the gene that produces filaggrin, a protein essential for building that outer barrier. Without enough filaggrin, the skin can’t hold moisture properly, loses water faster than it should, and becomes more permeable to irritants and allergens.
Filaggrin also breaks down into compounds that keep the skin’s surface slightly acidic, which is important because that acidity helps enzymes do their job maintaining the barrier’s fatty layer. When the pH shifts, those enzymes don’t work as well, the barrier weakens further, and a cycle begins: dry, cracked skin lets irritants in, which triggers inflammation, which damages the barrier even more.
Not everyone with eczema has a filaggrin mutation, but nearly everyone with eczema has some degree of barrier dysfunction. That’s why so many different triggers can set off a flare. They all exploit the same underlying weakness.
Soaps, Detergents, and Household Products
Surfactants, the foaming agents in soaps, shampoos, and cleaning products, are among the most common flare triggers. Sodium lauryl sulfate (SLS), found in everything from dish soap to body wash, destabilizes the skin barrier by raising its pH, breaking down structural proteins, and disrupting the enzymes that help skin cells mature normally. In higher concentrations, SLS produces effects on healthy skin that closely resemble the barrier disruption already present in eczema.
Hard water makes the problem worse. When you wash with a surfactant in hard water (water high in calcium and minerals), more of that surfactant gets deposited on your skin and stays there after rinsing. The residue continues irritating your skin long after you’ve toweled off. If you live in a hard water area and notice flares after bathing, the combination of your cleanser and your water supply could be the issue. Switching to a surfactant-free cleanser or installing a water softener are two practical steps worth trying.
Bacteria on Your Skin
Between 70% and 90% of people with eczema carry Staphylococcus aureus on their affected skin, compared to roughly 20% to 30% of the general population who carry it only in the nose. This isn’t a coincidence. S. aureus binds more efficiently to eczema-affected skin because the inflammatory environment increases the number of receptors the bacteria can latch onto.
Once established, S. aureus makes flares worse in two ways. It produces proteins that act as “superantigens,” essentially tricking the immune system into launching a disproportionately large inflammatory response. It also secretes enzymes that actively break down skin barrier proteins, increasing permeability and letting more allergens and pathogens through. This is one reason eczema flares can escalate quickly: the bacteria and the damaged barrier feed each other in a loop. Keeping affected skin clean and well-moisturized helps limit bacterial colonization, and some dermatologists recommend dilute bleach baths for this reason.
Stress and the Itch-Scratch Cycle
Stress doesn’t just make you feel worse. It physically changes your skin. When you’re under psychological stress, your body activates its stress-response systems, releasing hormones and signaling molecules that promote inflammation throughout the body, including in the skin. Stress impairs skin barrier function, slows wound healing, and increases the release of inflammatory compounds that can directly trigger or worsen eczema.
The itch side of eczema also has a stress connection. Inflammatory molecules produced during flares directly stimulate sensory nerves in the skin, creating that intense, hard-to-ignore itch. Scratching damages the barrier further, which increases inflammation, which increases itch. This itch-scratch cycle is one of the most frustrating aspects of eczema, and stress lowers the threshold at which it kicks in.
Food Triggers
The relationship between food and eczema is real but often overstated. The foods most commonly reported as triggers include dairy, eggs, peanuts, seafood, gluten, sugar, and alcohol. True food allergies (where the immune system reacts to a specific protein) can absolutely worsen eczema, and this is more common in young children with moderate to severe disease.
However, eliminating foods without guidance can backfire. Many people with eczema restrict their diets based on suspicion rather than confirmed allergy, which can lead to nutritional gaps without improving their skin. If you consistently notice flares within hours of eating a specific food, that’s worth investigating with allergy testing. Broad elimination diets, on the other hand, rarely help and can make things harder in the long run.
Clothing and Fabrics
What you wear sits against your skin all day, so fabric choice matters. Rough or loosely woven fibers create friction that irritates already-sensitive skin. Traditional wool is a classic offender because its coarse fibers poke and scratch, though ultra-fine or super-fine merino wool is a notable exception and is actually the least likely wool variety to cause itching.
Chemical finishes are another hidden trigger. Fabrics labeled “wrinkle-free” or “stain resistant” typically contain formaldehyde resins, which can irritate eczema-prone skin. Look for clothing labeled 100% organic cotton or certified OEKO-TEX, which indicates the fabric has been tested for allergenic dyes and chemical residues. Washing new clothes before wearing them also helps remove manufacturing chemicals.
Hormonal Shifts
Hormonal changes are an underrecognized trigger, particularly for women. Estrogen and progesterone influence immune cells involved in skin barrier function, and fluctuations in these hormones can directly provoke flares. About 47% of women with eczema report worsening symptoms in the week before their period, when estrogen drops sharply.
This hormonal connection also explains why some women experience eczema returning later in life. Perimenopause and menopause bring sustained hormonal shifts that can reactivate eczema that had been dormant for years. The common belief that eczema is mainly a childhood condition doesn’t hold up to the data. A large global survey found that the age group with the highest eczema prevalence in most regions was actually 41 to 64 years old, not children.
Weather and Temperature Extremes
Cold, dry air strips moisture from the skin’s surface faster than it can be replaced, which is why winter is peak flare season for many people. Low humidity indoors, courtesy of central heating, compounds the problem. On the other end of the spectrum, heat and sweating can trigger flares too. Sweat contains salts and compounds that irritate broken skin, and overheating increases itch.
The practical takeaway: moisturize more aggressively in winter, keep indoor humidity between 30% and 50%, and in summer, rinse sweat off quickly and wear breathable fabrics. Your skin barrier is constantly responding to the environment around it, and these adjustments reduce the daily load of stress it has to handle.
Layering Triggers Is What Causes Most Flares
Most flares aren’t caused by one thing in isolation. They happen when multiple triggers stack up. You might tolerate moderate stress on its own, or a slightly irritating laundry detergent on its own, but combine the two with poor sleep and dry winter air and your skin barrier can’t keep up. This is why flares sometimes seem random: it’s not always the last thing you touched or ate. It’s the accumulation.
Keeping a simple log of your flares, noting what you ate, your stress level, the weather, any new products, and where you are in your menstrual cycle if applicable, can help you identify your personal pattern. Over time, most people find they have two or three dominant triggers, and managing those makes the biggest difference.