12-phase flow (12)

1. 1FRAME
   Frame as an EXPOSURE-DRIVEN eczematous disease where allergen/irritant identification + avoidance is the definitive treatment and topical/systemic therapy is symptom control while avoidance takes effect. Separate ICD (innate, dose-dependent, burning≈itch, sharp contact-site margins, no sensitisation) from ACD (delayed type-IV, requires prior sensitisation, intense itch, may spread beyond site, id-reaction). Patch testing is the key ACD tool. Severe acute (rhus periorbital/airway), erythroderma, and occupational-disabling presentations are recognised here and escalated/routed.
   advance: contact framing set; ICD-vs-ACD axis + avoidance-as-definitive-treatment + escape routes noted
2. 2ENTRY
   Recognise an eczematous rash whose distribution maps to a contact exposure, or the recalcitrant/superimposed-dermatitis or severe-acute-ACD entries; capture distribution + margin character up front (geometric/linear → contact).
   inputs: lesion_distribution_and_margin
   actions: workup.chronic_pruritus
   advance: contact entry trigger present; distribution + margin recorded
3. 3CONTEXT
   Build the ICD-vs-ACD context: itch vs burning quality, spread beyond contact site / id reaction, prior sensitisation vs dose-dependent exposure, a structured occupational + personal-product/medicament allergen-exposure inventory, and atopic diathesis (impaired barrier ↑ both; ACD superimposed on AD is common). The exposure inventory directly shapes the supplemental patch-test series and the avoidance plan.
   inputs: itch_vs_burning_quality, spread_beyond_contact_site, prior_sensitisation_or_re_exposure, occupational_exposure_inventory, personal_product_and_medicament_inventory, atopic_diathesis
   actions: workup.chronic_pruritus
   advance: ICD-vs-ACD pretest prior + exposure inventory + atopy context established
4. 4RED_FLAGS
   Severe acute widespread ACD with facial/periorbital oedema or airway involvement (e.g. rhus/poison-ivy) → systemic corticosteroid + ED. Contact-dermatitis erythroderma (>90% BSA, airborne/systemic contact dermatitis) → thermoregulatory/fluid risk + admission. Secondary infection of excoriated dermatitis (honey-crust, pustules, weeping) → anti-staphylococcal therapy. These are recognised here and escalated/routed.
   inputs: periorbital_or_airway_oedema, erythroderma_extent, secondary_infection_signs
   actions: panel.cbc, panel.inflammation
   advance: severe-acute-ACD / erythroderma / secondary-infection screened and escalated/routed if present
5. 5INITIAL_WORKUP
   Contact dermatitis is diagnosed clinically + by patch testing for ACD — no blood test confirms it. Targeted workup: KOH/scraping to exclude tinea (a key contact-dermatitis mimic), and pre-systemic safety labs (CBC, LFT, creatinine) only if a chronic steroid-sparing systemic is anticipated for refractory disease. Skin biopsy is non-specific (spongiotic dermatitis) and used mainly to exclude other dermatoses.
   inputs: cbc_with_differential, lft
   actions: panel.cbc, panel.lft, panel.renal
   advance: tinea excluded as indicated; pre-systemic safety labs drawn only if chronic-systemic escalation likely
6. 6BRANCHING_WORKUP
   PATCH TESTING is the central branch for ACD: T.R.U.E. test (rapid, limited 35-allergen panel) vs comprehensive/extended NACDG ~80-allergen or ACDS Core series + occupation/product-specific supplemental trays (ACDS 2020 PMID 32947457). Apply ICDRG grading; read at Day-2 AND Day-4(-7) (early-only reading misses ~30% of relevant reactions); assign relevance (current/past/unknown). ROAT for weak/1+ leave-on reactions; photopatch if photodistributed; KOH if annular/scaly. Test validity is conditional: defer if active back dermatitis / recent systemic steroids / recent UV (false negatives + "angry back" false positives). Refer for patch testing if recalcitrant, occupational, or superimposed on another dermatosis.
   inputs: photodistribution_pattern, patch_test_concurrent_active_dermatitis
   actions: workup.chronic_pruritus
   advance: patch-test strategy selected (or deferred for valid conditions); relevant allergens + relevance assigned OR ICD/alternative dermatosis assigned + routed
7. 7DIFFERENTIAL
   Terminal contact-dermatitis differential with named pivots: ACD vs ICD (sensitisation history + spread-beyond-contact + patch-test pivot) vs atopic dermatitis (flexural + atopy + childhood onset pivot — route derm.atopic-dermatitis.core.v1; ACD frequently superimposed) vs nummular eczema (discrete coin lesions pivot) vs seborrheic dermatitis (greasy scale scalp/nasolabial pivot) vs psoriasis (sharp salmon plaque + silver scale + nail pits pivot — route derm.psoriasis.core.v1) vs tinea (KOH-positive annular advancing scale pivot) vs cellulitis (acute red-hot tender, portal + pain>itch pivot — route derm.cellulitis.core.v1) vs photoallergic/phototoxic contact dermatitis (photodistribution + photopatch pivot) vs systemic contact dermatitis (ingested/systemic exposure to a contact allergen, baboon syndrome/SDRIFE pivot).
   advance: ACD vs ICD assigned (or both); coexisting endogenous dermatosis flagged; relevant allergen(s) named when ACD
8. 8RISK_STRATIFICATION
   Severity = extent × site (hand/foot/face/eyelid functional impact) × chronicity × occupational disability. Localised mild → topical-only + avoidance; widespread or hand/foot functionally disabling or occupational → optimised topicals ± phototherapy ± systemic; severe acute widespread ACD → short systemic corticosteroid; chronic recalcitrant despite avoidance + topicals → patch test (if not done) + steroid-sparing systemic. Occupational hand dermatitis triggers an occupational-medicine / return-to-work + workers-comp pathway.
   inputs: lesion_distribution_and_margin, occupational_exposure_inventory
   advance: severity tier + occupational-disability overlay + escalation decision assigned
9. 9TREATMENT
   Step 1 — IDENTIFY + ELIMINATE the trigger (the non-pharmacologic decision gate beneath every step): allergen/irritant avoidance, substitution, barrier protection (gloves, barrier creams), emollients, workplace substitution/ergonomics. Step 2 — topical anti-inflammatory: mid/high-potency TCS (triamcinolone; clobetasol short burst for thick hand/foot/lichenified); low-potency hydrocortisone or topical calcineurin inhibitor (tacrolimus/pimecrolimus) for face/eyelid/folds — and note corticosteroid CONTACT ALLERGY (tixocortol-21-pivalate / budesonide markers) which can perpetuate "treatment-resistant" dermatitis. Step 3 — phototherapy (nbUVB/PUVA) for chronic hand/refractory disease. Step 4 — systemic: short oral corticosteroid for severe/widespread acute ACD with an ADEQUATE ≥10-14 d taper (too-short bursts cause rebound in rhus ACD — Curtis 2014 PMID 25247016), then steroid-sparing for chronic refractory: dupilumab (emerging, esp. chronic/occupational ACD when avoidance impossible), cyclosporine, methotrexate, azathioprine, alitretinoin (chronic hand eczema where available), mycophenolate. Gate on pregnancy/age/renal/hepatic.
   inputs: pregnancy_lactation, age, creatinine
   advance: trigger-elimination plan defined; appropriate ladder step started; adequate steroid taper if acute severe ACD; systemic agent gated on pregnancy/age/organ function
10. 10DISPOSITION
    Almost entirely outpatient/derm-clinic. ED/admission only for: severe acute widespread ACD with periorbital/airway oedema (stabilise + systemic steroid), contact-dermatitis erythroderma with thermoregulatory/fluid compromise, or severe secondary infection failing oral therapy. Patch testing, the avoidance plan, and the chronic ladder are outpatient; occupational disabling disease → occupational-medicine + return-to-work referral.
    inputs: periorbital_or_airway_oedema, erythroderma_extent
    advance: disposition documented; admission only for severe-acute/erythroderma/failed-infection criteria; derm + occupational follow-up arranged
11. 11MONITORING
    Disease: re-assess at the patch-test reading schedule (Day-2 + Day-4(-7)) then clinically at 4-12 wk to judge response to avoidance + ladder step (avoidance benefit accrues over weeks-months; persistent dermatitis despite documented strict avoidance argues an unidentified allergen, ICD, an endogenous dermatosis, or corticosteroid contact allergy). Drug safety: short systemic steroid course completion + rebound watch; steroid-sparing systemics — cyclosporine BP + creatinine (calc.ckd_epi_2021) q2wk during titration; methotrexate/azathioprine CBC + LFT; dupilumab conjunctivitis surveillance (no routine labs).
    inputs: creatinine, cbc_with_differential
    actions: panel.cbc, panel.lft
    advance: patch-test relevance + clinical response re-assessed at the appropriate interval; systemic-agent safety labs on schedule
12. 12FOLLOWUP
    Chronic-disease maintenance: written allergen/irritant avoidance plan with named allergens + cross-reactors + safe-product list (Contact Allergen Management Program / safe-list), barrier-protection + emollient habit, occupational return-to-work + workplace-substitution plan and workers-comp documentation where applicable, education on delayed re-exposure flares and id reactions, and re-patch-test criteria if a new pattern emerges. Dermatology continuity for any systemic agent; reassess for superimposed ACD if a sibling-engine dermatosis remains recalcitrant.
    inputs: occupational_exposure_inventory, personal_product_and_medicament_inventory
    actions: workup.chronic_pruritus
    advance: avoidance + safe-product + barrier + occupational/return-to-work plan documented; re-test + sibling-recalcitrance criteria set