Diagnostic Criteria for Atopic Dermatitis
Atopic dermatitis is diagnosed clinically based on the presence of pruritus plus three or more of the following: history of flexural involvement, personal or family history of atopy, general dry skin in the past year, visible flexural eczema (or age-appropriate distribution), and onset in the first two years of life. 1
Essential Clinical Features
The diagnosis requires no laboratory testing or skin biopsy and is based entirely on clinical presentation 1. The American Academy of Dermatology recommends a streamlined approach that is practical for clinical settings and applicable across all age groups 1.
Mandatory Criterion
- Pruritus (itching) is the hallmark feature and must be present, either reported by the patient or observed as scratching/rubbing behavior in children 1
Major Criteria (Need 3 or More)
History of flexural involvement: Itchiness in skin creases such as elbow folds, behind knees, or around the neck (or cheeks in children under 4 years) 1
Personal or family history of atopy: History of asthma or hay fever in the patient, or history of atopic disease in a first-degree relative for children under 4 years 1
General dry skin (xerosis) in the past year 1
Visible flexural eczema: Age-appropriate distribution—flexural surfaces in older children and adults, or cheeks/forehead/outer limbs in children under 4 years 1
Early onset: Disease beginning in the first two years of life (though not always applicable in children under 4 years) 1
Age-Specific Distribution Patterns
The morphology and location of lesions vary significantly by age, which is critical for accurate diagnosis 1:
Infancy: Typically starts on cheeks and extends to neck, trunk, and extensor surfaces of extremities, with notable sparing of the diaper area 1
Childhood and adolescence: More localized and chronic, commonly affecting flexor surfaces of extremities 1
Adults: Often presents with lichenification and chronic plaques in flexural areas 1
Clinical Morphology
Lesions vary by chronicity 1:
Acute lesions: Erythema, edema, papules, vesiculopapules, oozing, and crusting 1
Chronic lesions: Lichenification, excoriations, prurigo nodules, scales, and crusts 1
Chronic or Relapsing Course
Duration requirements differ by age 1:
- Infancy: Symptoms present for more than 2 months 1
- Childhood and adolescence: Symptoms present for more than 6 months 1
Important Diagnostic Considerations
No biomarkers are required or recommended for diagnosis 1. Specifically, routine IgE levels should not be obtained as they do not reliably distinguish atopic dermatitis from other conditions 1. While elevated IgE is commonly associated with AD, it is neither sensitive nor specific enough for diagnostic purposes 1.
Differential Diagnosis
Before confirming atopic dermatitis, exclude these conditions 1:
Seborrheic dermatitis in infancy: Unlike AD, it affects groin and axillary regions and is not pruritic 1
Contact dermatitis: May coexist with or exacerbate AD 1
Scabies: Look for burrows in finger webs 1
Immunodeficiency states: Consider if there are recurrent systemic infections, ear infections, or petechiae 1
Cutaneous T-cell lymphoma in adults, particularly if not responding to therapy 1
Nutritional or metabolic disorders in children 1
Clinical Pitfalls
If previously stable eczema deteriorates despite appropriate therapy, reassess the diagnosis 1. This deterioration may indicate secondary bacterial infection (suggested by crusting or weeping), herpes simplex infection (grouped punched-out erosions or vesiculation), or development of contact dermatitis 1.
Lymphadenopathy in AD patients is usually secondary to extensive skin disease and not indicative of systemic pathology, though it may cause initial concern 1.
The UK Working Party criteria, while validated for epidemiologic studies, cannot be applied to very young infants without modification 1. The revised American Academy of Dermatology criteria are more suitable for clinical practice across all ages 1.