How eczema begins

Eczema starts when your skin barrier — the outermost layer that holds moisture in and irritants out — becomes damaged or doesn't work properly. This allows water to escape and harmful substances to enter, causing inflammation, itching, and the red, cracked patches you see. The damage can happen because of your genes, your environment, or usually a combination of both.

Most people don't wake up one day with eczema fully formed. Instead, it develops gradually. You might notice your skin getting itchy and dry in one spot, then it spreads or flares up when you're exposed to a trigger — something like harsh soap, stress, or cold weather. Over time, if the barrier stays damaged, the itching and inflammation become a recurring pattern.

Key Takeaways

  • Eczema develops when your skin barrier weakens, allowing moisture to escape and irritants to enter, which causes inflammation and itching.
  • Genes play a major role — if your parents have eczema, allergies, or asthma, you are more likely to develop it.
  • Environmental triggers like soaps, detergents, stress, humidity changes, and allergens can start or worsen eczema flares.
  • Eczema often appears first in infancy or early childhood, though it can start at any age.
  • The condition is not contagious and does not mean your skin is dirty or infected, though scratching can lead to infection.

The role of your genes

Your DNA makes you more or less likely to develop eczema. If one parent has eczema, your risk is higher. If both parents have it, your risk is even higher. The same genes that increase eczema risk also make you prone to allergies and asthma — these three conditions often run together in families.

Genes control how your skin produces a protein called filaggrin, which helps hold the outer layer together and keeps it waterproof. If you inherit a variation in the filaggrin gene, your skin barrier may not form correctly, making it easier for moisture to leak out and irritants to get in. This genetic weakness is often present from birth, but eczema may not show up until something in your environment triggers it.

Environmental triggers that start or worsen flares

Even if you have the genes for eczema, you may never develop it unless something in your surroundings sets it off. Common triggers include harsh soaps and detergents, which strip away the skin's natural oils; low humidity or cold weather, which dries skin out; sweat and heat, which can irritate already sensitive skin; and fragrances or dyes in lotions, perfumes, and laundry products.

Allergens like dust mites, pet dander, pollen, and mold can trigger flares in some people. Stress and lack of sleep also play a role — when you're stressed, your immune system reacts more strongly, and inflammation increases. Certain fabrics like wool or synthetic materials that don't breathe well can irritate the skin and start a flare. For many people, eczema begins after a combination of these factors hit at once — for example, winter cold plus a new laundry detergent plus a stressful period at work.

When eczema typically first appears

Most people develop eczema before age five, often in infancy. A baby might develop red, itchy patches on the face, hands, or diaper area within the first few months of life. The skin may look dry and cracked, and the baby may scratch constantly, which can lead to infection if the skin breaks open.

Eczema can also start later in childhood or even in adulthood, though this is less common. Adult-onset eczema may be triggered by a major life change — a move to a different climate, a new job with different stress levels, pregnancy, or exposure to a new irritant at work. Some people have a mild form as a child that goes away, then eczema returns in adulthood when triggered by a new environment or stressor.

How your immune system contributes

Your immune system plays a central role in eczema. In people with eczema, the immune system overreacts to irritants and allergens that wouldn't bother most people. When your skin barrier is weak and irritants get through, immune cells in your skin release chemicals that cause inflammation. This inflammation makes the skin red, swollen, and itchy.

The itching then drives you to scratch, which damages the skin further and allows more irritants and bacteria to enter. This creates a cycle: weak barrier → irritants get in → immune overreaction → inflammation and itching → scratching → more damage to the barrier. Breaking this cycle is why treatment focuses on repairing the barrier with moisturizers and reducing inflammation with topical steroids or other medications.

Why eczema is not an infection

Eczema itself is not caused by bacteria, viruses, or fungi, so it is not contagious. You cannot catch it from someone else or give it to them. It is an inflammatory condition that starts with a faulty skin barrier and an overactive immune response.

However, because eczema makes your skin itchy and cracked, scratching can break the skin open and allow bacteria to enter, leading to a secondary infection. Signs of infection include increased warmth, pus, crusting, or swollen lymph nodes. If you suspect your eczema has become infected, see a doctor, as you may need antibiotics.

Frequently Asked Questions

Can eczema start from poor hygiene or dirty skin?

No. Eczema is not caused by dirt or lack of cleanliness. In fact, over-washing or using harsh soaps can trigger or worsen it. The condition starts with a genetic weakness in your skin barrier combined with environmental triggers, not from poor hygiene.

If I have eczema genes, will I definitely develop it?

Not necessarily. Having the genes increases your risk, but eczema may never develop if you are not exposed to the right triggers. Some people with a family history of eczema never get it, while others develop it only after a specific environmental change or stressor.

Can stress alone cause eczema to start?

Stress alone is unlikely to cause eczema in someone with no genetic predisposition, but it can trigger a flare in someone who already has the condition or is at risk. Stress weakens your immune system and increases inflammation, which can activate dormant eczema or make existing eczema worse.

Does eczema always start in childhood?

Most eczema begins before age five, but it can start at any age. Adult-onset eczema is less common but does happen, often triggered by a major change in climate, stress, or exposure to a new irritant. Some adults had mild eczema as children that resolved, then it returns later in life.

If my baby has eczema, will it go away?

Many children with eczema see improvement or complete resolution by their teens, though some carry it into adulthood. Early treatment and learning to manage triggers can reduce flares and help the skin heal. There is no cure, but the condition is very manageable with the right care.