How Is Eczema or Atopic Dermatitis Diagnosed?

No single test can diagnose atopic dermatitis. In fact, a diagnosis for this skin condition requires a careful, multifaceted investigation of signs and symptoms.

Atopic dermatitis is the most common type of eczema, a condition that causes symptoms including dry, scaly, itchy skin.

It is also the most severe and chronic (long-lasting) form of eczema, and the terms “eczema” and “atopic dermatitis” are often used interchangeably.

Atopic dermatitis is characterized by inflamed skin that may crack and release a clear fluid when scratched, an effect known as weeping. Other common symptoms of atopic dermatitis include:

• Discoloration — eczema typically appears reddish on white skin and violet, ash gray, or dark brown on skin of color
• Cracked skin behind the ears
• Rash, typically on the cheeks, arms, or legs
• Small, pus-filled bumps (if the skin is infected)

These symptoms may not show up all the time. People with atopic dermatitis experience flares, or periods when symptoms appear and worsen, followed by remissions, during which symptoms clear up.

There are many different possible triggers for atopic dermatitis flares (which differ from person to person), including:

• Stress
• Allergens, such as pollen, pet dander, and mold
• Dry skin
• Chemical irritants like dish soap and household cleaners
• Infections
• Hormones
• Changes in temperature (1)

Careful review of symptoms and triggers can help doctors differentiate atopic dermatitis from other types of eczema.

It’s critical to receive an atopic dermatitis diagnosis from a dermatologist, who can tell you which of the many different types of eczema you have. (2) The treatment you need will depend on the kind of eczema you have. Types of eczema include:

Contact eczema or contact dermatitis A localized skin reaction to a substance in the environment that causes skin to become inflamed and itchy. Most often, the skin immediately reacts to irritants, such as chemicals (acids, cleaning agents, soaps), abrasion, or heat, and is thus known as irritant contact eczema. Other times, the skin reacts slowly (up to 21 days) after contact with a substance that the immune system recognizes as foreign or allergenic, such as poison ivy, nickel, or latex; this is called allergic contact eczema. (3)

Hand eczema A form of eczema that is sometimes mistaken for simple dry skin, it produces dry, thick, scaly patches on the hands that may crack and bleed. Like contact eczema, hand eczema is triggered by various irritants and allergens. As such, it is most often found in people who work in cleaning, catering, hairdressing, healthcare, and mechanical jobs. (3,4)

Seborrheic dermatitis A chronic condition in which white or yellow scaly patches of skin develop in oily areas, such as the scalp (as dandruff), face, and ears. Unlike many other forms of eczema, seborrheic dermatitis is not a type of allergic or irritant reaction, and microorganisms that live on the skin (such as some types of yeast) can contribute to the condition. (5)

Dyshidrotic eczema This type of eczema causes small blisters on the edges of the fingers, toes, palms, and soles of the feet that are intensely itchy. Stress, allergens, and moist hands and feet are all potential triggers, as is exposure to nickel (either in everyday objects like jewelry and keys or in foods like chocolate and canned goods), cobalt (such as in metal-plated objects and foods like clams, red meat, and green vegetables), and chromium salts used in manufacturing things like cement, mortar, and anticorrosive products. (6)

Stasis dermatitis is a skin condition that develops when blood flow and pressure issues in the legs cause fluid to leak out of the veins and into the skin, resulting in ankle swelling, scaling, itchiness, and pain. Stasis dermatitis is usually a sign of an underlying issue, such as kidney failure, congestive heart failure, and obesity. (7)

Nummular eczema Another common type of eczema, nummular eczema is less likely to be confused with atopic dermatitis because it looks different from other types, appearing instead as itchy, coin-shaped lesions on the skin. (8)

There is no single test to diagnose atopic dermatitis or other types of eczema. Instead, diagnosis is based on personal and medical family history — and even then there’s a risk you’ll be misdiagnosed. (9)

According to diagnostic guidelines from the American Academy of Dermatology, there are a few essential features that must be present for someone to be diagnosed with atopic dermatitis — specifically severe itching (pruritus) and eczematous lesions that are either acute, subacute, or chronic. (10)

Acute lesions appear as a patchy discoloration and an oozing rash of blisters. Subacute lesions are discolored, dry, and scaly, while chronic lesions are indistinct lesions with scaly patches and plaques that are thick and leathery. (11)

These symptoms must be chronic or relapsing and follow age-specific patterns, including:

• Skin lesions on the face, neck, and extensor areas of joints (muscles that extend or straighten the upper and lower limbs) in infants and children
• Lesions that affect skin folds or flexures of joints, such as the backs of the knees and elbow creases, for all age groups
• No lesions in the groin and armpit regions of the body
• Lesions that localize to the face and neck, and often the hands, of adolescents and adults

A diagnosis of atopic dermatitis is further bolstered by evidence of extreme skin dryness, symptoms that appear early on in life (typically in the first year), and a personal or family history of allergic reactions and immunoglobulin E (IgE) antibodies to allergens.

During diagnosis, doctors may also look for several other associated features to help detect atopic dermatitis, such as:

• Pale skin
• Skin blanches that last for an unusually long time
• A raised rash that changes color from rubbing or scratching
• Pityriasis alba, which is characterized by dry patches on the face and upper arms
• Keratosis pilaris, which are small, rough bumps on the upper arms and thighs that develop from an overproduction of the protein keratin
• Ichthyosis (skin resembling fish scales)
• Increased lines on the palms
• Changes to the skin around the eyes, eyelids, eyebrows, and lashes
• So-called “chicken skin” or “goose-bump skin”
• Skin thickening
• Prurigo lesions, which are very itchy, firm nodules

But these associated features are only used in diagnosing atopic dermatitis in the hospital — they are too nonspecific for use in research and clinical studies. (10,11,12,13)

Doctors may perform a skin biopsy or other tests to rule out other health conditions that could be responsible for symptoms. These conditions include:

• Other types of eczema, in particular seborrheic dermatitis and contact dermatitis
• Scabies
• Psoriasis
• A type of dry, scaly skin condition called ichthyosis
• Immune deficiency diseases
• Cutaneous T-cell lymphoma, a rare type of cancer in which the immune system attacks the skin
• Photosensitivity dermatoses, which is a rash that develops in response to exposure to ultraviolet A (UVA) radiation, UVB radiation, and sometimes to visible light
• Various other causes of skin discoloration (10)