How Atopic Dermatitis (Eczema) Is Diagnosed

Diagnostic signs and evaluations can vary by age

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

Self-Checks

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.

While eczema can appear anywhere on the body, it tends to develop in specific patterns in different age groups. Symptoms can appear very early in life or develop during childhood, adolescence, or adulthood.

Age-Specific Eczema Patterns
Age Group Affected Areas
Infants Face, trunk (except the diaper area), and extensor surfaces (e.g., the front of the knee or back of the elbow or forearm)
Children  Wrists, ankles, flexor surfaces (such as the back of the knee or crease of the forearm)
Adolescents and adults Face, neck, hands

Another tell-tale sign in all age groups is the absence of rash in either the groin or armpits.

If you have symptoms like these, make an appointment to see your doctor and detail as much as you can about what you've observed.

When to Call a Doctor

Call your doctor immediately if a rash develops quickly, covers large portions of the body, starts to blister, or is accompanied by fever or pain. Any new rash in babies or younger children should also be reported without delay.

Physical Examination

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Atopic dermatitis
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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. The diagnosis of eczema is largely based on your medical history and a visual examination of the rash.

Diagnostic Criteria

Even medical professionals can sometimes have difficulty diagnosing atopic dermatitis. Because there are no tests available to diagnose the condition, certain criteria must be met in order for a diagnosis to be considered definitive.

Several standards and guidelines for the diagnosis of atopic dermatitis have been published, all of which are substantially the same as those established in the 1930s. In 1977, the Hanifin and Rajka diagnostic criteria for atopic dermatitis was introduced and remains the most commonly used guidelines for dermatologists.

Eczema is diagnosed based on how many "major" and "minor" features a person has. To be definitively diagnosed, you 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: A skin condition characterized by patches of lighter skin
  • Ichthyosis: A skin condition characterized by severe dryness and scaling
  • Hyperlinear palms and soles: Dry, prominent, permanent creases in the palms and soles
  • Keratosis pilaris: Fine, flesh-colored or reddish plugs primarily on the face, buttocks backs of the arms, or the outside of the thighs
  • Cheilitis: Scaliness of the lips and the skin at the corner of the mouth
  • Dennie-Morgan lines: Creases below the lower eyelids
  • Dark circles around the eyes ("allergic shiners")
  • Nipple eczema
  • Hand or foot dermatitis
  • Susceptibility to skin infections
  • Positive allergy skin tests

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 where the cause of the rash is in question. Diagnostic testing is needed more often for adults than for young children for several reasons.

Atopic dermatitis is incredibly common in young children and usually presents in a typical fashion. Because of this, children can usually be diagnosed by a visual examination alone.

By contrast, atopic dermatitis doesn't usually appear for the first time in adulthood (although it can). When it does, adults are more likely to have eczema appear in a non-typical pattern (such as on the hands).

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

KOH testing, also known as skin scraping, 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

Skin prick tests may also be used to determine if an allergy is a cause of your symptoms, although there is a possibility of false-positive results. 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.

RAST 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 far less accurate than skin prick tests.

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 a typical pattern, it can be harder to diagnose when it occurs atypically. In such cases, a differential diagnosis may be needed to exclude all other causes.

Some conditions that have similar symptoms to atopic dermatitis include:

All of these rashes cause itchy, inflamed skin but have different causes and treatments. It is important to get the correct diagnosis so that you can get started with the most effective treatment possible.

If in doubt about a diagnosis, do not hesitate to seek a second opinion. In some cases, a skin condition may be secondary to another disease and require an entirely different diagnostic approach.

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