Doctors can use a variety of diagnostic tools to help diagnose eczema, including a physical exam, lab testing, and more.

Eczema is a chronic skin disease that causes symptoms such as inflammation, intense itchiness, and changes in skin color around the affected patches.

Of the seven types of eczema, atopic dermatitis is the most prevalent. In fact, these two terms are often used synonymously. Eczema most commonly develops during infancy and childhood, but may occur at any age.

If you or a loved one has unexplained skin symptoms that may point to eczema, a doctor will need to run certain tests and determine other criteria to make an accurate diagnosis. They may also refer you to a dermatologist or an allergist to treat your condition.

Learn more about these eczema diagnostic tools, as well as possible preventive and treatment options for future flare-ups.

Eczema is primarily diagnosed with a physical exam.

People who have eczema often experience dry skin and intense itchiness, which can sometimes even keep them awake at night. In addition to your symptoms, a doctor will look at your skin during an examination to look for signs of eczema. These may include:

  • scaly skin patches
  • rashes that can vary in color depending on skin tone, including red, purple, or brown
  • swelling and inflammation
  • thickening skin from recurring rashes
  • cuts, scabs, and infections from scratching the affected areas of skin

The site of the skin rashes can also provide clues as to whether eczema is the culprit.

  • Infants tend to get eczema on the face and scalp.
  • Children tend to get eczema on the face, elbows, and knees.
  • Adults tend to get eczema in the creases of the skin, as well as the face, neck, and knees.

Both your personal and family medical history can help a doctor determine your risk for developing eczema.

For example, it’s estimated that about half of all people who have atopic dermatitis also have asthma, hay fever, or food allergies.

Also, since eczema can run in families, having a family history of this condition can also be a possible indication that the itchy skin rashes you’re experiencing could indeed be eczema.

In some cases, a doctor may need to order certain tests to confirm eczema and to rule out other possible causes of your itchy skin rashes. This can also help them differentiate between atopic dermatitis and other possible types of eczema.

Allergy tests

Allergy tests can help determine whether eczema and other allergy symptoms might be attributed to certain triggers in your environment. Among these are pollen, mold, pet dander, and dust mites.

Allergy testing is commonly conducted via a skin prick test. It’s important to note that, while this test may determine substances you might be allergic to, experts do not recommend this type of assessment for eczema alone.

You may also require patch testing, which can help identify substances that may be causing a type of eczema known as allergic contact dermatitis.

Blood test

Blood tests are usually not used to help diagnose eczema. In some cases, however, a doctor may order blood testing to help rule out allergies that you may have alongside eczema.

For example, an allergy blood test may measure immunoglobulin E (IgE) levels. IgE is a type of antibody that can cause allergy symptoms due to your immune system’s reactivity to certain substances, including pollen, dust, certain foods, and more.

Biopsy

Less commonly, a dermatologist may order a skin biopsy to confirm an eczema diagnosis. This involves taking a sample of the affected skin and sending it to a lab for further analysis.

Along with possible clinical testing, a dermatologist or primary care doctor might diagnose eczema based on the following criteria:

  • chronic or severe skin itchiness
  • a rash that is also a different color than your natural skin tone
  • scaly, and sometimes oozy lesions
  • self-reported and physical signs of an “itch-scratch cycle,” meaning that scratching the itchy eczema rashes can worsen the skin barrier and lead to more itching
  • age-specific patterns and affected locations of skin

Such criteria can help a doctor rule out other causes of your symptoms. Some examples and their differences include:

  • Contact dermatitis: This acute rash can develop at any age, and is caused by direct contact with a chemical or other skin irritant
  • Psoriasis: Psoriasis is another immune-mediated condition that is more likely to develop during adulthood. Psoriasis rashes may also be covered with silvery scales.
  • Seborrheic dermatitis: Unlike atopic dermatitis, skin rashes associated with seborrheic dermatitis tend to be oily, yellow-colored, and crusty. It affects the scalp and face, and may develop in all ages, with “cradle cap” affecting infants.
  • Tinea corporis: Also called ringworm, this common fungal infection is common in children and can cause circular, scaly rashes.

Eczema is primarily diagnosed by examination of the skin and self-reported symptoms. A primary care provider or a specialist, such as a dermatologist, may perform this.

In some cases, though, a doctor may want to use other diagnostic tools to help confirm eczema and rule out other possible skin conditions. Allergy testing is also used if you have a personal or family history of allergies.