Introduction: When to Seek Diagnostic Evaluation
If you or your child experience persistent itchy, dry, or inflamed skin that doesn’t improve with basic care, it may be time to seek medical evaluation. Atopic dermatitis (also called atopic eczema) is the most common form of eczema, affecting roughly 10 to 30 percent of children and 2 to 10 percent of adults in developed countries. The condition typically begins in early childhood, with approximately 60 percent of cases starting before one year of age.[1][6]
You should consider seeking diagnostic evaluation if you notice a rash that is intensely itchy, appears on typical areas like the inside of elbows or behind knees, or if the skin becomes dry, cracked, or discolored. In babies and young children, the rash often appears on the face first, then spreads to the neck, scalp, arms, and legs. For older children and adults, the rash tends to show up in fewer spots, particularly where the skin bends or flexes.[1][2]
It’s especially important to see a healthcare provider urgently if the affected skin becomes blistered, crusty, starts leaking fluid, has spots filled with pus, feels painful or warm, suddenly worsens, or if you develop a fever. These signs may indicate that your eczema has become infected or that you’ve developed a more serious complication called eczema herpeticum, which requires immediate medical attention.[4][17]
Classic Diagnostic Methods
The diagnosis of atopic dermatitis is primarily based on clinical evaluation rather than laboratory testing. Your healthcare provider will start by talking with you about your symptoms, examining your skin carefully, and reviewing your personal and family medical history. This conversation and physical examination are often sufficient to make an accurate diagnosis.[11][21]
According to guidelines established by the American Academy of Dermatology in 2014, doctors consider several key features when diagnosing atopic dermatitis. Essential features that must be present include persistent itchiness and the presence of eczema with typical appearance and location patterns appropriate for the patient’s age. In children, this often means involvement of the face, neck, and outer surfaces of limbs, while in any age group, the condition commonly affects areas where skin bends, such as the inside of elbows and behind knees. The groin and underarm areas are typically spared.[8][18]
Important features that support the diagnosis include an early age when symptoms first appeared, a personal or family history of atopy (the tendency to develop allergic conditions like asthma, hay fever, or food allergies), and the presence of extremely dry skin called xerosis. If one parent has atopic conditions, there’s more than a 50 percent chance their children will develop atopic symptoms; if both parents are affected, up to 80 percent of their children may be affected.[6][8]
Associated features that are nonspecific but suggest the diagnosis include unusual vascular responses (such as facial pallor or delayed blanching when pressure is applied), conditions like keratosis pilaris (small bumps on the skin, often on arms or thighs), thickened skin with increased skin markings called lichenification, changes around the eyes, and darkening of the skin in affected areas.[8][18]
During the physical examination, your doctor will look at the appearance, location, and characteristics of your rash. Atopic dermatitis can present in three clinical phases. The acute phase shows vesicular (small fluid-filled blisters), weeping, and crusting eruptions. The subacute phase presents with dry, scaly, red or discolored raised areas. The chronic phase demonstrates lichenification from repeated scratching. The appearance varies based on your skin tone: on light skin, the rash may look red, while on dark skin, it may appear darker than the surrounding skin, brown, purple, or gray.[2][3]
Additional Testing When Needed
In most cases, no laboratory tests or imaging studies are necessary to diagnose atopic dermatitis. However, your doctor may recommend additional tests in certain situations to identify allergies, rule out other skin diseases, or determine if specific triggers are worsening your condition.[11][21]
If your doctor suspects that certain foods are triggering your or your child’s rash, they may recommend allergy testing. It’s important to note that not all people with atopic dermatitis have allergies, although the condition is associated with increased IgE (immunoglobulin E) levels in many cases. IgE is an antibody involved in allergic reactions. Food hypersensitivity may cause or worsen atopic dermatitis in 10 to 30 percent of patients, with 90 percent of such reactions caused by eggs, milk, peanuts, soy, and wheat.[6][8]
Patch testing may be performed on your skin to help identify specific types of allergies causing dermatitis. In this test, small amounts of different substances are applied to your skin and then covered. Over the next few days, your doctor examines your skin during follow-up visits for signs of a reaction. This testing is particularly useful for identifying contact dermatitis, which occurs when your skin reacts to specific allergens or irritants like fragrances, preservatives, or certain metals.[11][21]
Blood tests may be ordered in some cases to check for elevated IgE levels or peripheral eosinophilia (increased numbers of a type of white blood cell called eosinophils in the blood), both of which are commonly seen in atopic dermatitis. However, these findings are not specific to atopic dermatitis and may be present in other allergic conditions as well.[8][18]
If your healthcare provider is uncertain about the diagnosis or suspects another skin condition, they may perform a skin biopsy, though this is not routinely necessary for atopic dermatitis. A biopsy involves removing a small sample of skin tissue for examination under a microscope. This procedure helps distinguish atopic dermatitis from other conditions that may look similar, such as psoriasis, seborrheic dermatitis, or contact dermatitis.[3][8]
Diagnostics for Clinical Trial Qualification
When patients are being considered for enrollment in clinical trials studying new treatments for atopic dermatitis, more standardized and detailed diagnostic procedures are typically required. Clinical trials need precise measurements to assess disease severity accurately and to track how well experimental treatments work compared to existing options.
The diagnostic criteria used for clinical trial qualification generally follow the same essential features required for standard clinical diagnosis: the presence of itching and eczematous skin changes with typical patterns. However, clinical trials often require additional documentation and measurements to establish a baseline severity level and to ensure participants meet specific inclusion criteria.[8][18]
One key aspect of clinical trial diagnostics is the assessment and grading of disease severity. Researchers use various validated scoring systems to measure the extent and severity of atopic dermatitis. These systems evaluate factors such as the percentage of body surface area affected, the intensity of symptoms like redness, thickness, scratching marks, and the impact on quality of life. Asking about the presence and frequency of symptoms allows physicians to grade the severity of the disease and monitor response to treatment over time.[3]
Clinical trials may require comprehensive allergy testing to understand each participant’s atopic profile. This might include skin prick tests to identify environmental allergens, blood tests measuring total and specific IgE levels, and documentation of any co-existing allergic conditions like asthma, allergic rhinitis (hay fever), or food allergies. Understanding these factors helps researchers determine if certain patient subgroups respond differently to treatments.[5][6]
Some clinical trials investigating the underlying mechanisms of atopic dermatitis may require more specialized testing. This could include blood tests to measure levels of specific immune cells like eosinophils, various cytokines (proteins that regulate immune responses), or other biomarkers related to inflammation. Genetic testing may be performed in research settings to identify mutations in genes like filaggrin, which plays a crucial role in maintaining the skin barrier. People with filaggrin mutations have an impaired ability to form and repair the protective outer layer of skin, making them more susceptible to atopic dermatitis.[5][6]
Before enrolling in a clinical trial, participants typically undergo thorough screening to rule out other conditions and to ensure they don’t have active skin infections. This may involve visual examination by dermatology specialists, photographic documentation of affected areas, and sometimes bacterial cultures if infection is suspected. Screening helps ensure that changes observed during the trial are due to the experimental treatment rather than other factors.[8]
Throughout the clinical trial, participants undergo regular diagnostic evaluations to monitor their response to treatment and to watch for any side effects. These assessments typically occur at scheduled intervals and use the same standardized measures employed at baseline, allowing researchers to track changes over time and compare outcomes between different treatment groups accurately.
