Atopic dermatitis (Eczema)

Introduction:

• Common inflammatory skin condition known as atopic dermatitis or atopic eczema.
• Characterized by widespread skin dryness, itching, and rashes.

Demographics:

• Affects approximately 230 million globally.
• Lifetime prevalence >15% in wealthier countries.
• Commonly starts in infancy; up to 20% of children affected.
• 80% develop condition before age 6.
• Persists in 5–15% of young adults up to 26 years old.

Causes:

• Results from a mix of environmental and genetic factors.

• No known single cause; likely represents multiple conditions
• Theories involve:
  • Immune system
  • Skin structural gene mutations
  • Keratinocyte defects
  • Skin surface microbiome (bacteria, viruses, yeasts)
  • Various other factors

Immune System Theory

• Primarily an immune system disease
• Critical cytokines:
  • IL-4 and IL-13 (Th2 pathway)
  • IL-22 (Th22 axis)
• Result in barrier defects and inflammation

What is Atopy?

• Tendency to develop asthma, eczema, and hay fever
• Mostly inherited (genetic)
• Overactive immune response to environmental factors
• Variability in development among individuals

Disease Manifestation and Triggers

• Affects the whole body, manifests in the skin
• Triggers include:
  • Viral infections
  • Teething
  • Certain foods
  • Unprovoked flares

Inherited Barrier Defect

• Associated with immune-mediated and inherited abnormalities
• Increased skin permeability and reduced antimicrobial function
• Main abnormality: filaggrin expression
  • Filaggrin gene (FLG) on chromosome 1 (1q21.3)
  • Abnormal filaggrin linked to severe, early-onset eczema

Consequences of Filaggrin Loss

• Corneocyte deformation
• Disrupted extracellular lipid organization
• Reduced natural moisturizing factors
• Increased skin pH, leading to serine protease activity and skin inflammation

Immune System Imbalance

• Imbalance between Th-1 and Th-2 lymphocytes
• Elevated Th-2 cells and associated cytokines
• High levels of IgE antibodies and eosinophils in some children

Th2 Cytokines Effects

• Water loss
• Increased permeability to irritants and allergens
• Enhanced response by Langerhans cells, worsening the barrier defect
• Reduced ceramide and filaggrin
• Increased bacterial colonization and infection

Microbiome Role

• Different organisms in body sites contribute to lesion distribution
• Flares linked to Staphylococcus aureus proliferation and microbiome dysbiosis
• Intestinal microbiome also under investigation

Factors Contributing to Dry Skin

• Winter weather
• Frequent washing, especially with hot water
• Hard water and soap
• Low humidity
• High temperatures
• Chlorine in swimming pools

Irritants

• Common irritants:
  • Soap
  • Harsh detergents
  • Coarse fibers (wool, synthetics)
  • Cosmetics and perfumes
  • Dusty environments

Infection Role

• Infective organisms trigger and aggravate eczema
• Prone to Staphylococcus aureus infections
• Herpes simplex virus, molluscum contagiosum, and viral warts are common
• Fungal infections like malassezia and candida are more likely

Allergens and Eczema

• Skin barrier defects can induce food allergies secondarily
• High false-positive rates in allergy tests
• Food allergies affect one-third of children with eczema
• Environmental allergens (grass, dust mites, cat dander) can trigger immediate reactions

Stress Impact

• Physical, mental, or social stress exacerbates eczema
• Common cold, social changes, and family conflict are potential stressors

Climate Influence

• Cold, damp climates worsen eczema
• Better in summer months due to ultraviolet light exposure
• Heat increases itching and redness

Investigations for Atopic Dermatitis

• No specific investigations usually required
• Useful occasional investigations:
  • Skin swabs for bacteriology: Identify methicillin-resistant strains of Staphylococcus
  • Viral culture: Confirm eczema herpeticum
  • Iron studies: Severe eczema can lead to iron deficiency; iron deficiency can worsen pruritus
  • Total IgE: Elevated levels confirm atopy; normal levels possible in non-allergic patients
  • RAST tests (specific IgE): Negative results have high predictive value; positive results less useful
  • Prick tests: Positive results may confirm atopic diathesis
  • Patch tests: Rule out specific contact allergies, e.g., to applied medicaments

Diagnostic Criteria for Atopic Dermatitis

• Itch: Persistent itching that may worsen with irritants or allergens.
• Typical Morphology and Distribution:
  • Infants: Cheeks, face, neck folds, scalp, and extensor surfaces.
  • Children: Flexures of limbs and groin.
  • Adults: Groin, hands, feet, and neck.
• Dry Skin: Commonly presents across all ages.
• History of Atopy: Personal or family history of allergic rhinitis, asthma, eczema, skin sensitivities, or urticaria.
• Chronic Relapsing Dermatitis: Recurrent episodes with identifiable triggers.
• Common Triggers:
  • Inhalant allergens especially house dust mite (which may also be a contact allergen)
  • Ingested allergens in some infants (eggs, milk, soybeans, peanuts and wheat account for most of these)
  • Irritants, especially skin dehydration by over-washing, woollen clothing
  • temperature extremes
  • sweating
  • sand pits
  • frequent washing or use of soap
  • chlorinated pools
  • infections – Staphylococcus aureus exotoxins, which act as superantigens
  • Emotional stress
  • irritants (such as clothing and detergents)
  • certain foods
  • scratching or rubbing
  • perfumes.
• Atopic eczema may be complicated by microbial colonisation or infection:
  • Staphylococcus aureus (impetiginised eczema)
  • Streptococcus pyogenes
  • Herpes simplex (eczema herpeticum)
  • Warts
  • Molluscum contagiosum
  • Malassezia spp.

Prognosis

• Most children experience significant improvement as they mature, with enhanced function of oil and sweat glands.
• Outcomes by Age:
  • 60% achieve normal skin by age 6.
  • 90% achieve normal skin by puberty.
• Chronic Concerns: Lichenification can occur with persistent atopic dermatitis.
• Complications:
  • Psychological impact, contact dermatitis, occupational skin disease.
  • Susceptibility to infections like Staphylococcus, herpes (eczema herpeticum), and molluscum contagiosum.

Treatment Recommendations

General Advice

• Skin Care:
  • Use low-pH, non-perfumed products (e.g., Dermaveen, Hamiltons, QV, Cetaphil)
  • Apply emollients like sorbolene with 10% glycerol or paraffin creams (e.g., Dermeze, QV moisturizing cream) immediately after bathing
• Emollients and Moisturisers
  • Essential for all dermatitis types; long-term use recommended
  • Regular application (2-3 times/day) even if skin appears normal
  • Adults with extensive eczema may need up to 500g weekly
  • Different formulations: leave-on products, soap substitutes, bath additives
  • High oil/low water mixtures preferred for hydration and barrier repair
  • Greasy moisturisers effective but may be uncomfortable; lighter moisturisers need frequent reapplication
  • Adverse effects: time-consuming application, residue, fire hazard from paraffin-based products, slipperiness, potential contact dermatitis from ingredients like sodium lauryl sulphate (SLS)

• Antiseptics
  • Used to treat/prevent infections due to skin colonization by bacteria (e.g., Staphylococcus aureus)
  • Common antiseptics:
    • Bleach bath: half a cup of household bleach in a full bath
    • Potassium permanganate: weak concentration (1 in 10,000 dilution) for wet soak/bath; short-term use
• Bathing:
  • Older children should take short, tepid showers.
  • Avoid extreme temperatures and overheating.
  • Opt for loose, cotton clothing.
• Environmental Controls:
  • Implement dust mite reduction strategies such as using premium grade dust mite covers for bedding,
  • washing linen in hot water (above 55°C), and replacing fabric upholstery and carpets.

Medications

• Coal Tar
  • Used in shampoos, lotions, creams; often mixed with topical steroids
  • Treats scaly atopic dermatitis; smell may be off-putting
• Antihistamines:
  • Sedating types (e.g., promethazine for children 12 years and older) can be used at night to manage itch.
• Antibiotics:
  • For patients at increased risk of secondary infections, use antiseptic washes and consider topical (e.g., mupirocin 2%) or systemic antibiotics (e.g., flucloxacillin, cephalexin).
• Antivirals:
  • Oral acyclovir may be necessary for herpes simplex virus complications.
• Corticosteroids:
  • Mainstay for mild-to-moderate atopic dermatitis
  • Use weakest effective steroid; consider skin site and severity
  • Fingertip unit guides application amount
  • Techniques to enhance effect:
    • wet wraps
    • paste bandages
    • steroid impregnated tape
  • Weekend treatment to maintain control and prevent flare-ups
  • Fear of steroids leads to inadequate use; incorrect use may cause rebound flare
  • Face and Flexures:
    • Start with 1% hydrocortisone (e.g., Sigmacort, Dermaid) and transition to more potent options like 0.1% methylprednisolone (Advantan) if necessary.
  • Body:
    • se moderately potent corticosteroids (e.g., Betamethasone valerate 0.02%, Methylprednisolone).
  • Thickened Skin:
    • Potent or very potent corticosteroids, such as Betamethasone dipropionate or Mometasone 0.1%, may be required.

Phototherapy

• Narrowband UVB phototherapy for severe cases
• Combined with topical treatments; not suitable for young children/infirm

Systemic Treatments for Atopic Dermatitis

Systemic Steroids

• Short course to control flare; useful for special occasions

Immunosuppressive and Anti-Inflammatory Agents

• Long-term control of severe disease
• Agents: methotrexate, azathioprine, ciclosporin, mycophenolate mofetil
• Require weeks to work; careful monitoring needed

Treatment for Infective Complications

Secondary Bacterial Infection

• Skin swabs to determine bacteria and antibiotic sensitivity
• Avoid topical antibiotics; consider topical antiseptic
• Oral antibiotics for overt Staphylococcal infection

Viral Infections

• Herpes simplex (eczema herpeticum): antiviral tablets/injections
• Molluscum contagiosum, coxsackievirus (eczema coxsackium): specific treatments

Staph Eradication

• Add 45ml of household bleach to a quarter-filled bath, soak for 5 minutes, avoiding facial immersion, rinse off, and immediately apply medications and moisturizers.