Eczema flares when your skin’s protective barrier is weakened and something irritating gets through. The triggers range from everyday products in your bathroom to the temperature of your shower water, and understanding which ones affect you most can significantly reduce how often and how severely your skin reacts.
At the root of most eczema is a shortage of a structural protein called filaggrin, which normally helps your outermost layer of skin hold moisture and keep irritants out. When filaggrin is deficient, your skin loses water faster, dries out more easily, and becomes far more permeable to allergens, bacteria, and chemicals. That compromised barrier is the reason so many different triggers can set off the same cycle of itching, redness, and inflammation.
Soaps, Detergents, and Chemical Irritants
The products you use to clean your skin and clothes are among the most common eczema triggers. Sodium lauryl sulfate (SLS), a foaming agent found in many body washes, shampoos, dish soaps, and laundry detergents, directly damages the proteins that hold your skin barrier together. In studies on healthy volunteers, just 24 hours of SLS exposure disrupted the barrier and altered how skin cells repaired themselves. If that’s the effect on healthy skin, the impact on eczema-prone skin is significantly worse.
SLS isn’t the only culprit. Many fragranced products, antibacterial soaps, and household cleaning agents contain surfactants and preservatives that strip the thin lipid (fat) layer protecting your skin. Switching to fragrance-free, sulfate-free cleansers is one of the single most effective changes you can make. The same goes for laundry detergent, since residue left on clothes and bedding sits against your skin for hours.
Hot Water and Long Showers
A hot shower might feel soothing in the moment, but it actively worsens eczema. Prolonged water exposure disrupts the outermost layer of skin, increasing its permeability to irritants and infections. And once skin temperature hits about 42°C (108°F), the itch threshold drops, meaning your skin becomes more reactive to even mild stimulation.
International clinical guidelines generally recommend keeping showers or baths to 5 to 10 minutes with warm water. European guidelines specifically suggest water temperatures between 27 and 30°C (about 80 to 86°F), while Japanese guidelines allow up to 36 to 40°C (97 to 104°F), calling that range optimal for skin barrier recovery. The key habit is applying moisturizer immediately after bathing, while your skin is still slightly damp, to lock in whatever moisture you’ve absorbed.
Clothing and Fabric Choices
The itchiness people associate with wool isn’t about wool itself. It’s about fiber diameter. When individual fibers are thick, their stiff ends poke out from the fabric surface and stimulate pain receptors in the skin, creating that prickly, irritating sensation. This happens with coarse wool, certain synthetics, and any loosely woven fabric with protruding fibers. The effect is purely mechanical and gets worse when you’re already inflamed.
Fine Merino wool with fibers 17.5 micrometers or thinner doesn’t trigger this prickle response. In clinical studies, people with eczema wore Merino wool base layers without worsening their symptoms. So the old advice to avoid all wool isn’t quite right. What matters is fiber thickness, not the type of animal it came from. Cotton and silk are also generally well tolerated, while rough polyester and acrylic blends tend to be problematic.
Allergens That Penetrate Damaged Skin
When your skin barrier has gaps, allergens that would normally sit harmlessly on the surface can slip through to deeper layers. Once there, immune cells recognize them as threats and launch an inflammatory response. This is why dust mites, pet dander, pollen, and mold can all trigger eczema flares, even though they aren’t directly irritating the way a chemical would be.
Dust mites are a particularly common offender. They thrive in bedding, upholstered furniture, and carpets. Their waste particles are small enough to penetrate compromised skin and activate immune cells that have been primed by previous exposures. For people sensitized to dust mites, the result is a flare that seems to come from nowhere, often worse at night when you’re lying in bedding full of allergen. Washing sheets weekly in hot water (at least 60°C/140°F) and using allergen-proof mattress covers can reduce this exposure significantly.
Weather and Humidity Swings
Cold, dry air in winter strips moisture from skin that’s already struggling to retain it. Indoor heating makes things worse by dropping humidity even further. Many people with eczema notice their worst flares between November and March for exactly this reason. The combination of cold outdoor air and heated indoor air creates a constant cycle of moisture loss.
Extreme heat and humidity can also trigger flares, but through a different mechanism. Sweating irritates already-inflamed skin, and the salt in sweat can sting broken areas. Rapid temperature changes, like going from a heated building into freezing air, seem to be especially provocative. Keeping indoor humidity around 40 to 50 percent with a humidifier during winter, and wearing breathable layers to minimize sweating in summer, helps buffer against both extremes.
Stress and Sleep Deprivation
Stress doesn’t cause eczema, but it reliably makes it worse. When you’re under psychological stress, your body produces more cortisol and other stress hormones that impair skin barrier repair and increase inflammatory signaling. This creates a vicious cycle: eczema causes stress, stress worsens eczema, and the resulting itch disrupts sleep, which further weakens immune regulation and barrier function.
Poor sleep alone can trigger flares. During deep sleep, your body does its most active tissue repair, including restoring the skin barrier. When nighttime itching fragments your sleep, that repair process is cut short. Keeping your bedroom cool, moisturizing before bed, and wearing soft, breathable sleepwear can help break the cycle.
Bacterial Overgrowth on the Skin
Healthy skin hosts a balanced community of bacteria, but eczema-prone skin tends to be dominated by Staphylococcus aureus. This bacterium thrives when the barrier is compromised and the skin’s natural acidity shifts. Once established, it produces toxins that directly trigger inflammation and further damage the barrier, creating a self-reinforcing loop of infection and flare.
Signs that bacteria may be worsening your eczema include yellow crusting, oozing, or sudden worsening that doesn’t respond to your usual moisturizing routine. Keeping skin well-moisturized helps maintain its natural defenses against bacterial overgrowth, and bleach baths (very dilute, about a quarter cup of household bleach in a full bathtub) are sometimes used to reduce bacterial load on the skin’s surface.
Food and Contact Allergens
Food allergies can worsen eczema, especially in young children, but the relationship is more nuanced than many people assume. The most common food triggers are cow’s milk, eggs, peanuts, soy, and wheat. However, food is a confirmed trigger in only a subset of people with eczema, and eliminating foods without proper testing often leads to unnecessary dietary restriction without improvement. If you suspect a food trigger, tracking flares alongside what you eat for a few weeks can help identify patterns worth investigating with an allergist.
Contact allergens are a separate category. Nickel (in jewelry, belt buckles, and phone cases), fragrances, rubber accelerators in gloves, and certain preservatives in skincare products can all cause delayed reactions that look identical to a regular eczema flare. If your eczema consistently worsens in areas that contact specific materials, patch testing can identify the exact allergen responsible.