Atopic Dermatitis | Eczema | Geeky Medics

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Introduction

Atopic dermatitis, also known as atopic eczema, is a chronic, relapsing, inflammatory skin condition that typically begins in infancy or early childhood.

Worldwide, 204 million people (2.6%) live with atopic dermatitis, making it the most common chronic inflammatory skin condition.^1-2 Of these, 103 million are children, while the rest are adults, with a male-to-female ratio of 1:1.13.^{1, 3}

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Aetiology

Atopy is defined as a genetic predisposition to an exaggerated immune response to specific environmental agents, characterised by the overproduction of immunoglobulin E. The atopic triad is a term used to collectively describe the development of:

The exact pathophysiological mechanism is not fully understood, however, a combination of a dysregulated immune system, environmental influences and a genetic predisposition is thought to cause a disrupted epidermal barrier.⁴

Pathophysiology

Table 1. Summary of the pathophysiology of atopic dermatitis^4-5

Factor	Description
Genetic predisposition	The main inherited abnormality identified is in the FLG gene, which codes for the development of filaggrin, a protein essential for the formation and function of the epidermal barrier.
Immune dysregulation	There is a dysequilibrium in T lymphocytes, with increased levels of Th-2 lymphocytes and their related cytokines, also contributing to a loss of skin barrier function.
Environmental influences	Multiple environmental factors, such as cold weather, low UV exposure, obesity and pollution, can trigger atopic dermatitis.

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Risk factors

Irritants

Specific irritants that can trigger exacerbations of atopic dermatitis, including:

• Soaps
• Detergents
• Alcohol-containing products
• Clothing materials (e.g. wool)
• Temperature extremes

While these substances can exacerbate atopic dermatitis, they are not generally classified as allergens because they do not typically elicit an immune response.⁴

Allergens

Contact, and occasionally food allergens, may trigger and worsen eczema in atopic patients.⁶ 

Common contact allergens include nickel, rubber products, hair dyes, perfumes and adhesives.

Skin infections

Those with atopic dermatitis are more susceptible to the development of specific infections, which can also trigger and exacerbate the condition.

These include:

• Bacterial: Staphylococcus aureus
• Viral: Herpes simplex virus, Poxvirus, Human papillomavirus
• Fungal: Malassezia⁴

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Clinical features

History

Symptoms typically present in childhood, during the first two years of life, but are also more common between 2 and 6 months.⁵ Atopic dermatitis follows a relapsing and remitting course, with acute flare-ups on a background of chronic inflammation.⁷

Typical symptoms of atopic dermatitis include:

• Pruritits 
• Erythema
• Oedematous papules
• Weeping and/or crusting lesions 
• Fissures
• Chronic fluctuating rash⁵

Other important areas to cover in the history include:

• Identification of triggers
• Past medical history (e.g. features of atopy)
• Family history (e.g. genetic predisposition)

Clinical examination

The clinical appearance of atopic dermatitis varies with age and can be divided into infantile, childhood, and adult phases.

Infantile phase

Typical clinical findings in infants include:

• Facial distribution: with relative sparing of the napkin area
• Involvement of extensor areas on crawling, e.g. knees and elbows 
• Exudative, crusted lesions on rubbing^{5, 7}

Childhood phase

Typical clinical findings in children include:

• Flexural distribution: mainly the antecubital and popliteal fossae
• Excoriations, crusting, hypopigmentation and hyperpigmentation
• Areas of vesiculation: as part of an eczematous reaction
• Lichenification: may occur from prolonged rubbing of the skin⁵

Adult phase

Typical clinical findings in adults include:

• Hand distribution: common due to domestic and occupational exposure
• Flexural distribution
• Vermillion of the lips and surrounding skin distribution
• Lichenification
• Localised involvement over the nipple and areola (more so in females)^4-5

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Differential diagnoses

Possible differential diagnoses in the context of suspected atopic eczema include:

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Investigations

Atopic dermatitis is generally a clinical diagnosis, and investigations are rarely required.

A wound swab is required if infection is suspected. 

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Diagnosis

The diagnosis of atopic eczema is made when a child has any 3 or more of the following in conjunction with pruritus:

• Onset of signs and symptoms, under 2 years of age
• Personal history of asthma or allergic rhinitis or a first-degree relative with a history of atopy
• If under 18 months of age, a history of either past or even active flexural, cheek or extensor dermatitis
• Dry skin over a period of the last 12 months⁶

Classification

The Eczema Area and Severity Index (EASI) is a standardised, validated tool for estimating eczema severity. This tool requires estimating the percentage of skin involvement in each of four body areas (head and neck, trunk, upper and lower extremities), along with scores for erythema, oedema, papules, excoriation, and lichenification.⁹

Eczema may also be classified by severity as mild, moderate or severe. This includes severity based on physical features, as well as on the impact of quality of life and psychosocial wellbeing.⁶

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Management

Conservative management

Conservative management of atopic dermatitis includes:

• Patient education and lifestyle advice: to prevent and manage exacerbations, and allow early recognition of infection
• Avoidance of triggers
• Avoidance of scratching: as this can worsen inflammation and increase the risk of infection

Medical management

Medical management of atopic dermatitis includes:

• Emollients: the mainstay of management, to be used during asympomatic periods and exacerbations. Emollient washes can be used instead of soaps.
• Topical corticosteroids: for active exacerbations, with potency dependent on severity and affected site
• Topical calcineurin inhibitors (e.g. tacrolimus): indicated only in moderate to severe eczema over 2 years old, where topical corticosteroids are ineffective and further use is contraindicated
• Antihistamines: for short-term use with severe itching or urticaria (non-sedating) or sleep disturbance (sedating)^{6, 10}

Specialist management

Specialist management is reserved for severe atopic dermatitis refractory to standard medical management, and may include:

• Oral prednisolone: for short-term use only
• Phototherapy (narrowband UVB): effective over several weeks for reducing disease activity; should not be initiated during acute flares
• Oral immunosuppressants (e.g. ciclosporin, methotrexate): for long-term control where other treatments are insufficient and quality of life is significantly affected
• Monoclonal antibodies (e.g. dupilumab): target the shared IL-4 receptor alpha subunit, blocking signalling from IL-4 and IL-13
• JAK inhibitors (e.g. baricitinib): use balanced against the risk of adverse effects^{6, 12-14}

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Complications

Bacterial infection

Secondary bacterial infection, commonly caused by Staphylococcus aureus or Streptococcus species, can lead to impetiginised atopic dermatitis. It may be difficult to distinguish from uninfected atopic dermatitis, and bacterial infection should be considered when eczema fails to respond to steroid monotherapy.⁶

Clinical features include:

• Weeping
• Pustules
• Crusting, typically honey coloured 
• Systemic upset, e.g. fever and malaise

A course of antibiotics, usually flucloxacillin, would be required.

Viral infection

Eczema herpeticum

Herpes simplex is also a common cause of infection in atopic dermatitis, and oral aciclovir should be used early to prevent the development of eczema herpeticum.⁶

Eczema herpeticum is a dermatological emergency and should be suspected in rapidly worsening, painful eczema, with clustering of vesicles and punched-out erosions, and systemic upset.⁶

Management is with intravenous aciclovir.⁸

Molluscum contagiosum

Molluscum contagiosum may have an exaggerated presentation in atopic children. Treatment should focus on treating the underlying atopic dermatitis.

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Reviewer

Dr Daniel Micallef

Consultant Dermatologist

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Editor

Dr Jamie Scriven

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References

1. British Journal of Dermatology. A study about how many people around the world have atopic dermatitis. 2024. Available from: [LINK].
2. Kolb L and Ferrer-Bruker SJ. Atopic Dermatitis. StatPearls. 2023. Available from: [LINK].
3. Tian J, Zhang D, Yang Y, et al. Global epidemiology of atopic dermatitis: a comprehensive systematic analysis and modelling study. British Journal of Dermatology. 2023. Available from: [LINK].
4. DermNet. Causes of atopic dermatitis. 2004. Available from: [LINK].
5. Griffiths C et al. Rook’s Textbook of Dermatology. 9th ed. 2016.
6. National Institute for Health and Care Excellence. Atopic eczema in under 12s: diagnosis and management (CG57). 2025. Available from: [LINK].
7. DermNet. Atopic Dermatitis. 2004. Available from: [LINK].
8. Primary Care Dermatology Society. Eczema – Paediatric (0-12yrs) – Primary Care Treatment Pathway. 2019. Available from: [LINK].
9. Hanifin JM, Baghoomian W, Grinich E, et al. The Eczema Area and Severity Index – A Practical Guide. Dermatitis. 2022. Available from: [LINK].
10. NHS. Atopic Eczema. 2024. Available from: [LINK].
11. DermNet. Guidelines for the diagnosis and assessment of eczema. 2014. Available from: [LINK].
12. DermNet. Treatment for atopic dermatitis. 2004. Available from: [LINK].
13. DermNet. Dupilumab. 2024. Available from: [LINK].
14. Nogueira M and Torres T. Janus Kinase Inhibitors for the Treatment of Atopic Dermatitis: Focus on Abrocitinib, Baricitinib, and Upadacitinib. Dermatology Practical & Conceptual. 2021. Available from: [LINK].

Image references

• Figure 1: DermNet. Infantile atopic dermatitis over the peri-oral area and cheeks. Licence: [CC BY-NC-ND 4.0].
• Figure 2. DermNet. Acute flexural atopic dermatitis. Licence: [CC BY-NC-ND 4.0].
• Figure 3. DermNet. Lichenified, flexural atopic dermatitis. Licence: [CC BY-NC-ND 4.0].
• Figure 4. DermNet. Eczema herpeticum. Licence: [CC BY-NC-ND 4.0].
• Figure 5. DermNet. Molluscum contagiosum over flexural atopic dermatitis. Licence: [CC BY-NC-ND 4.0].

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