What is eczema?

What is Eczema?

Eczema (also called dermatitis) is a chronic inflammatory skin condition characterized by itchy, dry skin with visible inflammation that appears as erythema and vesicles in acute phases, and as dryness, thickened skin (lichenification), and cracking in chronic phases. 1

Core Definition

The terms "eczema" and "dermatitis" are used interchangeably to describe a polymorphic pattern of skin inflammation. 1 This inflammatory response manifests differently depending on the stage:

Acute Phase Features 1

• Erythema (redness)
• Vesiculation (small fluid-filled blisters)
• Weeping and crusting

Chronic Phase Features 1

• Dryness (xerosis)
• Lichenification (thickened skin with accentuated markings)
• Fissuring (cracking)

Types of Eczema

Atopic Dermatitis (Atopic Eczema)

This is the most common form of eczema, accounting for the majority of cases. 1

Key characteristics include: 2, 3

• Chronic relapsing inflammatory skin disease
• Intense pruritus (itching) as the hallmark symptom
• Age-specific distribution patterns
• Strong association with personal or family history of atopy (asthma, allergic rhinitis, food allergies)

Prevalence: 2, 3

• Affects 10-20% of children globally
• Affects 2-3% of adults
• Approximately 80% develop symptoms within the first 5 years of life

Contact Dermatitis

This occurs when external agents trigger the inflammatory response. 1 Contact dermatitis includes:

• Irritant contact dermatitis (more common): Caused by direct chemical damage without immune involvement 1
• Allergic contact dermatitis: Involves T cell-mediated immune sensitization to specific allergens 1

Underlying Mechanisms

Atopic dermatitis results from complex interactions between: 2, 3

• Genetic susceptibility factors
• Environmental exposures
• Skin barrier dysfunction (increased water loss through the skin)
• Immunological derangement (abnormal immune responses)

The disease involves both "outside-in" mechanisms (where barrier breakdown allows allergen penetration) and "inside-out" mechanisms (where immune dysfunction triggers barrier disruption). 2

Clinical Presentation by Age

Infants and young children (under 4 years): 1, 4

• Lesions typically affect the cheeks, scalp, forehead, and outer limbs
• Diaper area is rarely involved

Older children and adults: 1, 4

• Lesions concentrate in flexural areas (folds of elbows, behind knees, neck)
• Head and neck involvement common

Diagnosis

Eczema is diagnosed clinically based on: 1, 2

• Patient history and symptoms
• Family history of atopic disease
• Physical appearance of the skin eruption
• Skin biopsy is generally not helpful

Diagnostic criteria require an itchy skin condition plus three or more of: 1

• History of itchiness in skin creases or cheeks (in young children)
• History of asthma, hay fever, or atopic disease in first-degree relatives
• General dry skin in the past year
• Visible flexural eczema (or cheek/forehead involvement in young children)
• Onset in the first two years of life

Common Complications

Skin infections are frequent complications: 2, 4

• Bacterial infection (especially Staphylococcus aureus) suggested by crusting or weeping
• Viral infections including herpes simplex (eczema herpeticum, which can be life-threatening)
• Deterioration in previously stable eczema may indicate secondary infection or development of contact dermatitis 1, 2

Associated Conditions

Adults with atopic dermatitis have increased risk of: 2

• Asthma (3 times more likely than general population)
• Food allergies (11% prevalence)
• More severe eczema correlates with stronger association with asthma

Impact

Eczema accounts for: 1, 2

• 4-7% of dermatological consultations
• 10-20% of all referrals to dermatologists
• Point prevalence of approximately 20% in the UK general population
• Significant impact on quality of life, sleep disturbance, and social functioning