Contact Dermatitis Causes and Characteristics

Introduction to Contact Dermatitis

Contact dermatitis is caused by external agents acting either as irritants or as allergens, where cell-mediated immune response is involved in the latter, affecting a significant portion of the population 1, 2
The British Journal of Dermatology guidelines suggest that contact dermatitis can result from a single overwhelming exposure or a few brief exposures to strong irritants or caustic agents, leading to acute irritant contact dermatitis 2, 3

Irritant contact dermatitis can be categorized into subjective irritancy, acute irritant contact dermatitis, and chronic (cumulative) irritant contact dermatitis, which occurs following repetitive exposure to weaker irritants 1, 2
Allergic contact dermatitis involves sensitization of the immune system to a specific allergen or allergens, with common allergens including nickel, fragrance compounds, cobalt, and p-phenylenediamine (PPD) 1, 2
Phototoxic, photoallergic, and photoaggravated contact dermatitis are triggered by light exposure to certain allergens 1, 3
Systemic contact dermatitis is seen after systemic administration of a substance to which topical sensitization has previously occurred 2, 4
Protein contact dermatitis results from repetitive handling of proteins, such as vegetables, meats, fish, flour, enzymes, and animal dander and fluids 1, 5

Soaps and detergents can damage the skin by causing denaturation of stratum corneum proteins, and changes in intercellular lipids can lead to decreased corneocyte cohesion and water-binding capacity 6
Hot water used for handwashing and low relative humidity are common irritants that can exacerbate contact dermatitis 6
Metals, such as nickel, and fragrances are common allergens that can trigger allergic contact dermatitis 1, 6, 7
Topical antibiotics, particularly in children, and rubber accelerators can also cause contact dermatitis 4

Contact dermatitis accounts for 4-7% of dermatological consultations, with irritant contact dermatitis being more common than allergic contact dermatitis 1, 2, 4
The point prevalence of hand dermatitis is approximately 2%, with a lifetime risk of developing hand dermatitis of 20% 1
Occupational factors play a significant role, with contact dermatitis making up approximately 70% of occupational skin disease 4
The prevalence of contact allergy to specific allergens in the general population in Europe is estimated at between 10% and 27% 1

Repeated exposure to irritants damages the skin barrier, changes skin flora, and results in more frequent colonization by staphylococci and gram-negative bacilli 6
Affected persons often complain of a feeling of dryness or burning, skin that feels "rough," and erythema, scaling, or fissures 6
In the acute phase, contact dermatitis is characterized by erythema and vesiculation, while in the chronic phase, it is characterized by dryness, lichenification, and fissuring 1

These symptomatic differences can help guide diagnosis when clinical features alone may be unreliable, as noted by the British Journal of Dermatology 8, 9

Allergic contact dermatitis usually carries a worse prognosis than irritant dermatitis unless the allergen is identified and avoided, according to the British Journal of Dermatology 8, 10
Irritant contact dermatitis results from direct chemical damage without immune system involvement, as reported in Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 11
Irritant contact dermatitis is more common than allergic dermatitis but generally has better prognosis if the irritant is removed, as stated by the British Journal of Dermatology 8

Clinical features alone are unreliable in distinguishing allergic contact from irritant and endogenous eczema, particularly with hand and facial eczema, as noted by the British Journal of Dermatology 8, 9
Patch testing is essential for confirming allergic contact dermatitis, with sensitivity and specificity between 70% and 80%, according to the British Journal of Dermatology 10, 12
The pattern and morphology of dermatitis is unreliable in predicting cause and distinguishing between different types of dermatitis, as reported by the British Journal of Dermatology 9

Patch testing should be performed when allergic contact dermatitis is suspected or cannot be ruled out, as recommended by the British Journal of Dermatology 8, 10

Water temperature above 40°C affects the skin barrier through lipid fluidization and disordered lipid structure, leading to increased skin permeability and irritation, according to the American Academy of Dermatology 13
Cold or very cold water for handwashing is specifically listed as a risk factor for inducing or worsening hand contact dermatitis, as stated by the American Academy of Dermatology 13
Using cold or lukewarm water for handwashing rather than hot water can help mitigate cold weather exacerbation, as water temperature does not affect microbe removal but does increase skin irritation, recommends the American Academy of Dermatology 13
Applying moisturizer after washing hands and before wearing gloves if needed can help prevent dryness and irritation, suggests the American Academy of Dermatology 13
Identifying and avoiding irritants, such as wet work and exposure to surfactants and detergents, is crucial in preventing contact dermatitis, advises the American Academy of Dermatology 13
More frequent handwashing during cold/flu season can compound irritant exposure without adequate barrier restoration, warns the American Academy of Dermatology 13