How Atopic Dermatitis (Eczema) Is Diagnosed

Atopic dermatitis

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There are no tests that can confirm a diagnosis of atopic dermatitis, more commonly known as eczema. Physicians use certain diagnostic guidelines that are based on how many major and minor features of atopic dermatitis a person has. Each person experiences a unique combination of these symptoms, which can vary over time. Patch testing, skin scraping, and other tests may be done to rule out other possible causes of rash.


It's estimated that many people with atopic dermatitis are undiagnosed. Some chalk their symptoms up to simply having dry or sensitive skin or believe that skin irritation has no treatment and is just something they 'have to live with.'

While eczema needs to be formally diagnosed by a doctor, the following are worth taking note of, as they may indicate the condition:

  • The rash is itchy, red, scaly, or blistered.
  • Dry skin never seems to resolve, even with regular application of moisturizing creams.
  • The rash seems to get better, but always returns.
  • It's a struggle to control the rash, even with good home care.

If these seem to apply to your case, make an appointment to see your doctor and detail as much as you can about what you've observed.

Call your doctor right away if the rash is painful, severe, covers large areas of the body, or is itchy to the point of disturbing sleep.

For infants or young children, the pediatrician should be called if they develop an undiagnosed skin rash, regardless of severity.

Physical Examination

If you think you have atopic dermatitis, you should be seen by a physician. Your regular healthcare provider can, in most cases, diagnose and treat atopic dermatitis. You may also be referred to a dermatologist.

Diagnosis of eczema is largely based on medical history and a visual examination of the rash.

Diagnostic Guidelines

Even medical professionals can sometimes have difficulty diagnosing atopic dermatits. Guidelines have been put in place to help with diagnosis.

A doctor diagnoses eczema based on how many "major" and "minor" features a patient has. To have atopic dermatitis, a patient must have three or more features from each of the two categories.

Major Features:

  • Intense itching
  • Characteristic rash in typical locations
  • Chronic or recurrent symptoms
  • Personal or family history of atopic dermatitis, hay fever, or asthma

Minor Features:

  • Early age at onset
  • Xerosis: Dry, rough skin
  • Pityriasis alba: Patches of lighter (hypopigmented) skin; more common in infants than older children
  • Ichthyosis: Severe dryness and scaling of the skin causing it to look like fish scales
  • Hyperlinear palms and soles: Dry, prominent, permanent creases in the palms and soles
  • Keratosis pilaris: Fine, flesh-colored or slightly red plugs on the backs of the arms, the outside of the thighs, buttocks, or face
  • Hand or foot dermatitis: Glistening red, scaling, and cracking skin on the hands or feet
  • Cheilitis: Scaliness of the lips and the skin in the corner of the mouth
  • Nipple eczema: Cracking and peeling of the skin of the areolae, most often in young girls at the start of puberty
  • Susceptibility to skin infections: Bacterial infections and viral infections like herpes simplex
  • Positive allergy skin tests
  • Dennie-Morgan lines: Creases below the lower eyelids
  • Dark circles around the eyes (allergic shiners): A blue-gray discoloration of the skin around the eyes, especially under the eyes, associated with nasal congestion

Labs and Tests

Even though testing can't detect whether or not you have eczema, your doctor may still run some to rule out other conditions. This is especially helpful in cases when the cause of the rash is in question. Diagnostic testing is needed more often for adults than for young children for several reasons.

First, atopic dermatitis is incredibly common in young children and it usually presents in a typical fashion. Because of this, it's easier to diagnose atopic dermatitis in children by means of a visual exam only.

Secondly, atopic dermatitis doesn't usually appear for the first time in adulthood (although it certainly can). Adults are more likely to have eczema appear in non-typical locations (i.e., not in the flexural areas).

Patch Tests

Patch testing is a non-invasive test used to check for substances you may have a reaction to when they come in contact with your skin. This test can specifically help diagnose contact dermatitis or differentiate between contact and atopic dermatitis.

The one caveat here is that people with atopic dermatitis are also very susceptible to developing contact dermatitis and vice versa. You can have both skin conditions, sometimes at the same time, which can complicate diagnosis.

Patch testing, though, can at least make you aware of common substances that may trigger a flare-up for you. This allows you to avoid those triggers and help prevent future symptoms.

Skin Scraping and Biopsy

Skin scraping (KOH testing) is a simple procedure used to diagnose fungal infections, such as ringworm. The skin is gently scraped with a scalpel, causing a small amount of dead skin to fall onto a slide. Potassium hydroxide (KOH) is added to the slide, which is then heated and observed under a microscope.

Skin biopsy is a test in which a small amount of skin tissue is removed and examined under a microscope. It's the standard diagnostic test used for dermatitis herpetiformis, an itchy eczematous rash associated with celiac disease.

Allergy Tests

Positive skin prick allergy test results are part of the diagnostic criteria possibilities listed above. However, the possibility of false positives needs to be kept in mind. A test may be positive not because it detects an allergy, but because overly sensitive skin that is exposed to multiple chemicals can become even more sensitive.

Blood tests that measure an allergic response in the blood may also be used. But these tests are not recommended in most cases because they are inaccurate in people with atopic dermatitis.

Differential Diagnoses

There are many different skin conditions that have similar symptoms. While the diagnosis of atopic dermatitis is fairly straightforward when the rash presents in typical locations and typical fashion, it can be harder to diagnose when it occurs atypically.

Some conditions that have similar symptoms include:

These rashes all will cause itchy, red, inflamed skin, but they all have different causes and different treatments. It's important to get the correct diagnosis so that you can get started with an effective treatment plan.

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