Occupational Dermatitis

Definition and Scope

• Fitzpatrick's Dermatology, Vol. 1&2, p. 468

Classification

Note: The North American Contact Dermatitis Group (NACDG) reported 60% ACD vs. 32% ICD among occupationally referred patients - selection bias toward tertiary referral centres may inflate ACD numbers.

• Fitzpatrick's Dermatology, p. 469-470

Etiology - Causative Agents

Physical Causes

• Heat (burns, hot tar, grease)
• Cold (Raynaud phenomenon, frostbite)
• Moisture / wet work (most common occupational exposure)
• Friction, pressure (calluses, corns)
• UV radiation, ionizing radiation

Chemical Causes

Fig. 16.2 - Causes of occupational contact dermatitis (UK). Dermatology 2-Volume Set, 5e

• Rubber: 23.4% of cases
• Nickel: 18.2%
• Epoxy and other resins: 15.6%
• Aromatic amines: 8.6%
• Chromate: 8.1%
• Fragrances and cosmetics: 8.0%
• Preservatives: 7.3%

• Dermatology 2-Volume Set 5e, p. 341-342; Andrews' Diseases of the Skin

Biological Causes

• Bacteria (Staphylococcus, Erysipelothrix, Bacillus anthracis)
• Fungi (Trichophyton, Candida)
• Mycobacteria (M. marinum - fish tank granuloma)
• Plant products (psoralens - phototoxic; Toxicodendron - ACD)

High-Risk Occupations

• Fitzpatrick's, p. 470-474; Andrews', p. 1200

Pathophysiology

Irritant Contact Dermatitis

• Direct disruption of the epidermal barrier by the irritant
• Causes release of cytokines (TNF-α, IL-1β, IL-6, IL-8) from keratinocytes
• Results in non-specific inflammation without immune memory
• Effects can be visible within minutes to hours
• Cumulative ICD: most common occupational pattern - repeated sub-threshold exposures to weak irritants (e.g., wet work) gradually lower the irritation threshold until dermatitis appears
• Filaggrin gene mutations markedly increase risk
• More than 57,000 chemicals known to cause ICD

Allergic Contact Dermatitis

• Type IV (delayed) hypersensitivity reaction
• Sensitization phase: hapten penetrates skin → binds to carrier proteins → processed by Langerhans cells → presented to T-lymphocytes → sensitized T-cells
• Elicitation phase: re-exposure → rapid T-cell response → inflammatory cascade
• Requires prior exposure; reaction appears 12-72 hours after re-exposure
• Only ~3700 chemicals are true sensitizers

Clinical Features

ICD - Clinical Spectrum

ACD - Clinical Features

• Pruritus (prominent), erythema, vesicles, weeping in acute phase
• Lichenification, fissuring, hyperpigmentation in chronic phase
• Site: Hands affected in 60% of ACD and 80% of ICD cases
• Spread beyond the primary contact site is common in ACD (airborne distribution pattern from paint sprayers, for example)
• Important clue: improvement during holidays/weekends away from work

Both ICD and ACD may present as:

• Acute, subacute, or chronic dermatitis
• Dyshidrotic (pompholyx) pattern (classically described in chromate allergy from cement)
• Discoid pattern

Differential Diagnosis

• Tinea manuum - may mimic hand dermatitis (especially post-steroid use); check KOH
• Scabies - interdigital involvement can simulate ICD
• Psoriasis - keratotic plaques on palms; nail involvement/IPJ plaques are clues; may be exacerbated by workplace trauma (Koebner)
• Porphyria cutanea tarda - blistering on dorsal hands (rarely mistaken for contact dermatitis)
• Endogenous eczema - coexisting atopic/dyshidrotic eczema, often multifactorial
• Dermatology 2-Volume Set 5e, p. 345

Contact Urticaria (Occupational)

• Immunologic contact urticaria (ICU): IgE-mediated; onset within 15-20 min; can progress to systemic anaphylaxis. Classic example: latex allergy in healthcare workers.
• Non-immunologic contact urticaria (NICU): No prior sensitization; localized; less severe; not inhibited by H1 antihistamines; responds to NSAIDs (prostaglandin pathway).
• Protein contact dermatitis: Chronic eczematous dermatitis with intermittent urticaria from protein exposure (food handlers, veterinary workers).
• SPT/prick testing (not patch testing) is used to diagnose immunologic contact urticaria.
• Fitzpatrick's, p. 474-480

Diagnosis

Occupational History (Key Points)

• Dermatology 2-Volume Set 5e, Table 16.2

Patch Testing (for ACD)

• Essential for any individual with potentially work-related dermatitis or for whom a job change is being considered
• Standard series + work-specific materials must be included (not all allergens are commercially available; MSDS may not disclose all ingredients)
• Testing 5200 chemicals with appropriate concentrations is feasible (guide published)
• When a reaction occurs to an unknown substance: dilutional series + testing ~20 controls confirms allergic vs. irritant reaction
• Applied to upper back; read at 48h and 96h (D2 and D4)
• Dermatology 2-Volume Set 5e, p. 342

Other Investigations

• KOH preparation - exclude tinea
• Skin biopsy - non-specific eczematous changes (spongiosis); may show birefringent fibers in fiberglass dermatitis under polarized light
• Skin prick test / SPT - for contact urticaria (IgE-mediated)
• RAST / fluorescence enzyme-labeled assay (FELA) - specific IgE measurement (RAST is largely replaced by FELA); used for ICU diagnosis
• Workplace visit - invaluable when occupational cause is suspected but not established from history alone
• Biomonitoring - e.g., urine arsenic speciation for arsenic exposure (inorganic arsenic is toxic; organic arsenobetaine is not)
• Fitzpatrick's, p. 479-481

Special Topics

Fiberglass Dermatitis

• Mechanism: direct mechanical penetration (proportional to fiber diameter >3.5 µm; inversely proportional to length)
• Features: pruritus, erythematous papules with follicular accentuation on exposed/forearm areas; paronychia common
• Diagnosis: tape stripping or KOH examination of skin scrapings
• Rapidly resolves after cessation of exposure; hardening occurs in most workers within weeks
• Dermatology 2-Volume Set 5e, p. 344

Chemical Burns (Occupational)

• Strong acids (sulfuric, nitric, HCl): coagulative necrosis; form barrier limiting penetration
• Hydrofluoric acid: liquefactive necrosis; penetrates to bone; pain lasting days; systemic toxicity if >1% BSA affected; treat with 2.5% calcium gluconate gel
• Strong alkalis (NaOH, wet cement): saponification of fatty acids → penetrate deeper than most acids; severe damage
• Phenolic compounds: nerve damage causing anesthesia without visible injury
• Initial treatment: copious irrigation with water; soap solution for water-insoluble chemicals; specific antidotes where available
• Dermatology 2-Volume Set 5e, p. 343-344

Occupational Skin Cancer

• UV radiation (natural + artificial) is the dominant cause
• UV increases 10-12% per 1000m altitude - airline pilots/cabin crew have 2-3x UV exposure at cruising altitude and twice the melanoma rate vs. general population
• Outdoor workers (agriculture, construction, fishing, landscaping) at highest risk
• Arsenic: occupational carcinogen; inorganic arsenic in urine is the reliable biomarker
• Fitzpatrick's, p. 477-478

Phototoxic Dermatitis

• Most occupational photosensitivity is phototoxic (not photoallergic)
• Common scenario: outdoor workers exposed to plant psoralens ("strimmer dermatitis" - plant sap splatter on inadequately protected skin)
• Coal tar/creosote: "tar/pitch smarts" - burning/stinging within 15 min of sun exposure
• Resolves with hyperpigmentation
• Dermatology 2-Volume Set 5e, p. 344

Management

Primary Prevention (Avoid Disease Onset)

• Engineering measures: enclose processes, improve ventilation, substitute less hazardous chemicals
• Chemical substitution: replace strong sensitizers/irritants with safer alternatives
• Pre-employment screening: exclude workers with severe childhood atopic dermatitis (especially with hand involvement) from "wet work" jobs; recommend "dry" work
• Education: workforce education in skin care reduces skin disease incidence (evidence-based)

Secondary Prevention (Early Detection)

• Health surveillance: periodic medical examination of all workers for early detection
• Prompt reporting of any skin irritation, however mild

Tertiary Prevention (Treatment of Active Disease)

• Eliminate or reduce exposure - most important step
• Appropriate PPE: gloves (select correct type per MSDS/manufacturer; replace regularly; each glove type has a defined penetration time for specific chemicals)
  • Acrylate glues, PPD (hair dye), glycerol monothioglycolate - rapidly penetrate latex gloves
  • Cotton inner liner if prolonged glove wear
• Avoid rings (chemicals accumulate underneath)
• Hand washing: use lukewarm water, dry thoroughly, attend to fingerweb spaces
• Barrier creams: for wet work (against acids, alkalis, water-based fluids) and dry work (against oils, greases, resins)
• Emollients: frequent application throughout the day

• Acute phase: topical corticosteroids (mainstay)
• Dry, fissured hands: soak in water 20 min at night → apply triamcinolone 0.1% ointment immediately (without drying) → hydrates and heals
• Maintenance: topical tacrolimus ointment, pimecrolimus cream + high-lipid content moisturizing creams
• Oral corticosteroids for severe acute ACD
• Andrews', p. 1207-1208; Dermatology 2-Volume Set 5e, Table 16.4-16.5

Prognosis

• ~10% develop persistent post-occupational dermatitis despite no identifiable ongoing cause
• Job change improves prognosis but does not guarantee resolution (new workplace may have same exposures; domestic exposure may perpetuate ACD)
• Prognosis is worse when allergen is present in both occupational AND domestic environments

• Atopic patients
• Males with chromate allergy
• Females with nickel allergy
• Delay in diagnosis before treatment
• Construction industry workers

• ICD from metalworking fluids
• Urushiol ACD in foresters
• ACD to acrylic monomers or amine curing agents
• Andrews', p. 1212; Dermatology 2-Volume Set 5e, p. 345

Medicolegal Aspects

• Occupational dermatitis has significant compensation and workers' disability implications
• Material Safety Data Sheets (MSDS) are legal documents that must disclose chemical composition and hazards (irritant, corrosive, sensitizer)
• Limitations of MSDS: may not list all relevant ingredients; manufacturer communication may be necessary
• Workplace visits and patch testing with work materials may be required for legal proceedings
• Systematic health surveillance in industry is often a statutory obligation (e.g., under the Factories Act - adequate washing facilities)
• Park's Textbook of Preventive and Social Medicine; Dermatology 2-Volume Set 5e

Summary Table: ICD vs. ACD at a Glance