Eczema (atopic dermatitis)

What it is

Atopic dermatitis, often called eczema, is a chronic (long-lasting) disease that causes inflammation, redness and irritation of the skin.¹ In most cases, there are periods when the disease is worse, called flares, followed by periods when the skin improves or clears up entirely, called remissions.¹ Eczema is a term for several different types of skin swelling, and the most common type is atopic dermatitis.³

No one knows what causes atopic dermatitis.¹ One explanation is a “leaky” skin barrier, which dries out and becomes prone to irritation and inflammation from many things in the environment.⁶ NIAMS says changes in genes, problems with the immune system and things in the environment may contribute to changes in the skin barrier.¹

It is a common condition that usually begins in childhood, but anyone can get it at any age.¹ The chance is higher with a family history of atopic dermatitis, hay fever or asthma.¹ Citing CDC reports on the United States for 2024, AAFA says that in 2024 over 9 million children had eczema, around 13 out of 100 children, and nearly 21 million adults had it, around 8 out of 100 adults.⁸

Symptoms

The most common symptom is itching, which can be severe.¹ AAAAI notes that eczema is sometimes described as an “itch which rashes,” and that the more a person scratches, the more severe the rash will be.⁶ Scratching leads to further redness, swelling, cracking, “weeping” clear fluid, crusting and scaling.¹

The rash tends to appear in different places at different ages.¹ During infancy and up to age 2, a red rash is most common on the face, the scalp and the skin around joints that touch when the joint bends.¹ During childhood, usually from age 2 to puberty, a red, thickened rash may appear on the elbows and knees (usually in the bend), the neck and the ankles.¹ In the teen and adult years, a red to dark brown scaly rash is most common on the hands, the neck, the elbows and knees (usually in the bend), the skin around the eyes, and the ankles and feet.¹ People with darker skin tones often see darkening or lightening of the skin where it is inflamed.¹

Contact dermatitis is a different skin reaction, one that appears when the skin comes in contact with an irritant or an allergen.⁷ Red, itchy bumps, especially at the site of contact with a possible irritant or allergen, may point to contact dermatitis.⁷ Infection can change how eczema looks: sometimes, especially when infected, the skin may have small, fluid-filled bumps that ooze a clear or yellowish liquid.⁷ Bacterial skin infections are common, can worsen from scratching and may make the disease harder to control, and viral skin infections like warts or cold sores can also occur.¹

NIAMS also lists sleep loss, hand eczema and eye problems such as pink eye (conjunctivitis) among the complications of atopic dermatitis.¹

What triggers it

AAAAI lists animal dander, pollens and dust mites among the potential triggers of atopic dermatitis, along with sweating, other infections, stress and contact with irritants like wool or soaps.⁵ AAFA’s list of common triggers also includes mold, pet (animal) dander, cold and dry air, air pollution, and certain chemicals, including fragrances and dyes.⁸ NIAMS names tobacco smoke, certain types of air pollutants, fragrances and other compounds found in skin products and soaps, and excessively dry skin as environmental factors that may trigger the immune system to change the skin’s protective barrier.¹

Foods are not common triggers of eczema, except rarely in infants and young children.⁵ Some young children with eczema can flare with a particular food, but food allergies causing eczema are much less common in older children and adults.⁶ Infection can set off a flare too: in children whose skin is oozing, crusting and painful, an infection may be the primary trigger.⁶

Food allergy, hay fever and asthma

Atopic dermatitis is often associated with other allergic diseases, such as food allergy, allergic rhinitis (hay fever) and asthma, and it has also been associated with eosinophilic esophagitis.⁵ Up to 30 percent of people with atopic dermatitis have food allergies, and up to 60 percent develop asthma or hay fever later in life.²

Atopic dermatitis is often the beginning of a series of allergic disorders referred to as the “atopic march.”² Researchers continue to study why having atopic dermatitis as a child can lead to the development of asthma and hay fever later in life.¹ In infants, NIAID’s guidance for parents names severe eczema, egg allergy or both as conditions that increase the risk of peanut allergy.⁹

When to see an allergist

AAAAI says it is important to see an allergist/immunologist for diagnosis and management of eczema, and that an allergist can help find out whether there is a trigger that can be avoided.⁶ It adds that infants and young children with more severe eczema should be evaluated for food allergy.⁶ An allergist can examine the skin and do testing to help work out the cause of a skin reaction.⁷

Allergy tests can mislead in eczema. NIAID says people with eczema are often diagnosed with allergies they may not have.¹⁰ They are likely to have high total IgE levels in general, resulting in positive allergy test results even though they may not actually have a food allergy.¹⁰ False-positive allergy tests can lead to an unnecessarily restrictive food-elimination diet, with unwanted outcomes such as malnutrition, weight loss or low weight gain.¹⁰

See a health care provider if a rash is bad, if it does not go away, or if other symptoms come with it.⁴ AAAAI says that when eczema “weeps,” or leaks fluid that crusts over when scratched, it is also infected.⁶ Skin conditions are one of the most common forms of allergy that an allergist/immunologist manages, so for questions about care, talk to an allergist.⁶