Atopic and Contact Dermatitis: Pathophysiology and Treatment
Dermatitis is a nonspecific term describing both acute and chronic skin reactions. Most dermatologists use
the term dermatitis to describe an acute, nonspecific skin reaction that exhibits swelling, erythema,
scaling, vesicles (blisters) and crusts.
Earliest and mildest symptoms of acute dermatitis:
- Erythema/redness caused by engorgement and dilatation of the small blood vessels
Severe symptoms of acute dermatitis:
- Vesiculation or blistering (skin cells form vesicles that fill with edema fluid)
- Breakage of blisters results in oozing/weeping, and evaporation of this fluid causes crusting,
scaling
Chronic dermatitis:
- Skin becomes dry, fissured, cracked
- Lichenification (extensive thickening of the skin) with prolonged itching and scratching. The skin
may show damage from scratching (linear or punctate scarring) and hyperpigmentation or
hypopigmentation.
Pathophysiology of Atopic Dermatitis (Eczema)
Pathophysiology
- The atopic triad consists of diseases that are characterized by mucocutaneous barrier dysfunction
o allergic rhinitis/conjunctivitis, asthma and atopic dermatitis.
- Atopic dermatitis = chronic, relapsing, inflammatory skin disease associated with the hyper-
reactivity of cutaneous and mucous membranes to environmental triggers that are innocuous to
nonatopic individuals.
- Underlying etiology atopic dermatitis = genetics resulting in a dysfunction of the epidermis
o Defect in the FLG gene results in filaggrin protein deficiency,
o Filaggrins are important for maintaining skin moisture. The breakdown of filaggrin is
required to form results in the production of hygroscopic free amino acids, which serve as
the major components of the skin's natural moisturizer factor (NMF).
o Decreased filaggrin → reduced NMF levels → inability of skin to maintain moisture/water
within the stratum corneum
o Loss of skin moisture → loss of skin barrier function → increased penetration of
environmental factors (irritants + allergens) → sensitization
o Once the skin has become sensitized to these environmental factors, re-exposure results in
an autoallergic stage characterized by inflammation and high IgE levels
o IgE triggers an eczema-type reaction rather than urticaria (hives)
Epidemiology
- Affects 10–20% of the population.
- Genetically associated; risk of 70% if both parents are afflicted; higher risk of inheritance from the
mother than the father
- More common in higher socioeconomic status
- In adults and children, Staphylococcus aureus colonization is high, whereas adult skin is more
heavily colonized with Malassezia yeasts.
, Atopic and Contact Dermatitis: Pathophysiology and Treatment
Atopic Dermatitis in Children…
- Predominantly a childhood disease
- Begins in infancy, but rarely present at birth
- ~80% of cases of atopic dermatitis develop in the 1st year of life and 90% of cases develop in the
first 5 years of life.
- In children younger than 2 years, males are more affected than females. In children older than 2
years, females are more affected. Female patients are more at-risk for chronicity.
o Note: Not all children who develop eczema during infancy will have eczema for the rest of
their life.
Clinical Presentation (typical eczema timeline)
1) Infantile: 80% (1-2 years) – Acute (i.e. eczema appears than goes away)
• Babies: cheeks are affected
• Age 2-3: scalp, neck, diaper area, extensors are affected
2) Children 4-5 years – Eczema comes back and becomes a chronic, relapsing disease
• Lichenified plaques/patches, dry, thick skin, neck, extremities, folds
• Affected areas: back of arms, front legs, elbows, knees, toes, wrists, ankles
3) Adolescents & Adults – Eczema starts to become more generalized, affecting a larger range of
skin; severity waxes and wanes
• Affected areas: face (periorbital), flexures, hands, anogenital
Signs & Symptoms
Atopic dermatitis presents as an intensely pruritic acute, subacute or chronic eruption.
- Itch = main symptom & is most intense at nighttime
o Itch may precede visible skin lesions and/or erythema, and inflammation may evoke
pruritus. Various triggers such as stress result in appearance of erythema followed by itch,
then vasodilation and inflammation due to scratching.
- Skin changes are induced by constant scratching and excoriations
- Skin is typically dry and lesions are scaly
o Acute stage: vesicular, weeping or oozing
o Chronic stage: less redness, increased dryness and early lichenification (thickened skin,
hyperpigmentation and accentuation of skin furrows due to repeated rubbing and scratching)
- Usually intermittent and leads to vigorous itch-scratch cycles, commonly with secondary bacterial
infection of excoriated lesions.
Red, vesicular, weeping/oozing → red, dry, scaly lesions → lichenification, hyperpigmentation
, Atopic and Contact Dermatitis: Pathophysiology and Treatment
Distribution
- Can affect any area of the body, but preferentially the flexures
and the face.
- Babies <6 months of age: face and scalp; redness and chapping
of a baby's cheeks can be the earliest sign; chapping usually
begins at 2–3 months and persists for 2 years.
- Remission usu. occurs b/w 2 and 4 years of age. Subsequently,
a chronically relapsing dermatitis begins, located on the extensor sides of the extremities &
flexural areas.
o Most common sites: flexural area of elbow and knee; mouth, eyelids, neck and hands;
lips can be dry & scaly.
- Chronic atopic dermatitis: first seen on back of the arms and front of the legs; later, transition
occurs to the elbows and knee folds.
- Frictional areas such as wrists and ankles are regular sites, and localization may occur to the toes.
Occlusive footwear causing excessive sweating and drying of the feet may exacerbate the condition.
- Children 4–6 years: symmetric eczema on flexural areas, hands, feet and the back of the thigh.
- As the child reaches adulthood, recurrent outbreaks diminish or disappear. In adolescents and
adults, the involvement may be generalized, but flexural accentuation is the hallmark of clinical
disease. Adults typically exhibit lesions on the face, upper body and flexural areas.
In summary, the areas of the body
that are affected by eczema tend to
differ based on the age.
Eyelid eczema (21% of adolescents)
- Associated with hay fever and exposure to aeroantigens such as house dust mites.
- Infra-auricular and retro-auricular sites of ears are particularly prone to fissuring in reaction to
minor trauma.
Atopic hand eczema typically involves the volar aspect of the wrists and the dorsum of the hands.
Concurrent foot eczema occurs in 1/3 of patients with atopic hand eczema.
Other minor features exhibited by atopic patients include recurrent conjunctivitis, cheilitis (chapped lips),
infraorbital folds (Dennie-Morgan lines), keratosis pilaris, nipple eczema, recurrent infections
(especially viral) and impaired cell-mediated immunity.
Dermatitis is a nonspecific term describing both acute and chronic skin reactions. Most dermatologists use
the term dermatitis to describe an acute, nonspecific skin reaction that exhibits swelling, erythema,
scaling, vesicles (blisters) and crusts.
Earliest and mildest symptoms of acute dermatitis:
- Erythema/redness caused by engorgement and dilatation of the small blood vessels
Severe symptoms of acute dermatitis:
- Vesiculation or blistering (skin cells form vesicles that fill with edema fluid)
- Breakage of blisters results in oozing/weeping, and evaporation of this fluid causes crusting,
scaling
Chronic dermatitis:
- Skin becomes dry, fissured, cracked
- Lichenification (extensive thickening of the skin) with prolonged itching and scratching. The skin
may show damage from scratching (linear or punctate scarring) and hyperpigmentation or
hypopigmentation.
Pathophysiology of Atopic Dermatitis (Eczema)
Pathophysiology
- The atopic triad consists of diseases that are characterized by mucocutaneous barrier dysfunction
o allergic rhinitis/conjunctivitis, asthma and atopic dermatitis.
- Atopic dermatitis = chronic, relapsing, inflammatory skin disease associated with the hyper-
reactivity of cutaneous and mucous membranes to environmental triggers that are innocuous to
nonatopic individuals.
- Underlying etiology atopic dermatitis = genetics resulting in a dysfunction of the epidermis
o Defect in the FLG gene results in filaggrin protein deficiency,
o Filaggrins are important for maintaining skin moisture. The breakdown of filaggrin is
required to form results in the production of hygroscopic free amino acids, which serve as
the major components of the skin's natural moisturizer factor (NMF).
o Decreased filaggrin → reduced NMF levels → inability of skin to maintain moisture/water
within the stratum corneum
o Loss of skin moisture → loss of skin barrier function → increased penetration of
environmental factors (irritants + allergens) → sensitization
o Once the skin has become sensitized to these environmental factors, re-exposure results in
an autoallergic stage characterized by inflammation and high IgE levels
o IgE triggers an eczema-type reaction rather than urticaria (hives)
Epidemiology
- Affects 10–20% of the population.
- Genetically associated; risk of 70% if both parents are afflicted; higher risk of inheritance from the
mother than the father
- More common in higher socioeconomic status
- In adults and children, Staphylococcus aureus colonization is high, whereas adult skin is more
heavily colonized with Malassezia yeasts.
, Atopic and Contact Dermatitis: Pathophysiology and Treatment
Atopic Dermatitis in Children…
- Predominantly a childhood disease
- Begins in infancy, but rarely present at birth
- ~80% of cases of atopic dermatitis develop in the 1st year of life and 90% of cases develop in the
first 5 years of life.
- In children younger than 2 years, males are more affected than females. In children older than 2
years, females are more affected. Female patients are more at-risk for chronicity.
o Note: Not all children who develop eczema during infancy will have eczema for the rest of
their life.
Clinical Presentation (typical eczema timeline)
1) Infantile: 80% (1-2 years) – Acute (i.e. eczema appears than goes away)
• Babies: cheeks are affected
• Age 2-3: scalp, neck, diaper area, extensors are affected
2) Children 4-5 years – Eczema comes back and becomes a chronic, relapsing disease
• Lichenified plaques/patches, dry, thick skin, neck, extremities, folds
• Affected areas: back of arms, front legs, elbows, knees, toes, wrists, ankles
3) Adolescents & Adults – Eczema starts to become more generalized, affecting a larger range of
skin; severity waxes and wanes
• Affected areas: face (periorbital), flexures, hands, anogenital
Signs & Symptoms
Atopic dermatitis presents as an intensely pruritic acute, subacute or chronic eruption.
- Itch = main symptom & is most intense at nighttime
o Itch may precede visible skin lesions and/or erythema, and inflammation may evoke
pruritus. Various triggers such as stress result in appearance of erythema followed by itch,
then vasodilation and inflammation due to scratching.
- Skin changes are induced by constant scratching and excoriations
- Skin is typically dry and lesions are scaly
o Acute stage: vesicular, weeping or oozing
o Chronic stage: less redness, increased dryness and early lichenification (thickened skin,
hyperpigmentation and accentuation of skin furrows due to repeated rubbing and scratching)
- Usually intermittent and leads to vigorous itch-scratch cycles, commonly with secondary bacterial
infection of excoriated lesions.
Red, vesicular, weeping/oozing → red, dry, scaly lesions → lichenification, hyperpigmentation
, Atopic and Contact Dermatitis: Pathophysiology and Treatment
Distribution
- Can affect any area of the body, but preferentially the flexures
and the face.
- Babies <6 months of age: face and scalp; redness and chapping
of a baby's cheeks can be the earliest sign; chapping usually
begins at 2–3 months and persists for 2 years.
- Remission usu. occurs b/w 2 and 4 years of age. Subsequently,
a chronically relapsing dermatitis begins, located on the extensor sides of the extremities &
flexural areas.
o Most common sites: flexural area of elbow and knee; mouth, eyelids, neck and hands;
lips can be dry & scaly.
- Chronic atopic dermatitis: first seen on back of the arms and front of the legs; later, transition
occurs to the elbows and knee folds.
- Frictional areas such as wrists and ankles are regular sites, and localization may occur to the toes.
Occlusive footwear causing excessive sweating and drying of the feet may exacerbate the condition.
- Children 4–6 years: symmetric eczema on flexural areas, hands, feet and the back of the thigh.
- As the child reaches adulthood, recurrent outbreaks diminish or disappear. In adolescents and
adults, the involvement may be generalized, but flexural accentuation is the hallmark of clinical
disease. Adults typically exhibit lesions on the face, upper body and flexural areas.
In summary, the areas of the body
that are affected by eczema tend to
differ based on the age.
Eyelid eczema (21% of adolescents)
- Associated with hay fever and exposure to aeroantigens such as house dust mites.
- Infra-auricular and retro-auricular sites of ears are particularly prone to fissuring in reaction to
minor trauma.
Atopic hand eczema typically involves the volar aspect of the wrists and the dorsum of the hands.
Concurrent foot eczema occurs in 1/3 of patients with atopic hand eczema.
Other minor features exhibited by atopic patients include recurrent conjunctivitis, cheilitis (chapped lips),
infraorbital folds (Dennie-Morgan lines), keratosis pilaris, nipple eczema, recurrent infections
(especially viral) and impaired cell-mediated immunity.
