Allergic contact dermatitis (ACD) is a type of contact dermatitis that results from an allergic reaction to a substance that has contacted the skin. It is a delayed cell-mediated hypersensitivity reaction. Patch testing is the gold standard for diagnosing ACD, as it can identify the specific allergen causing the reaction. Clinically, ACD presents as pruritic papules and vesicles on an erythematous base that can become erosions or crusts. Chronic cases result in lichenified pruritic plaques and scaling. Management involves identifying and avoiding the causal allergen as well as topical corticosteroids and other medications to reduce inflammation and itching.

1. ALLERGIC
CONTACT DERMATITIS (ACD)

2. INTRODUCTION
• Von Pirquet (1906) - Gk: ‘Allos’ = Other ; ‘Ergon’ – Work
• 1840 - Dakin  Dermatitis Venenata / Rhus dermatitis
• Bloch / Steiner-Worlich  Allergic Sensitization of skin
(Primula sp)
• Haxthausen (1942)  ‘Allergy stems from within’
• Landsteiner / Chase (1949) 
hypersensitivity reaction to HAPTENS
Cell-mediated
• Staedler (1847) – Blotting paper patch test ; modified by
Jadassohn – Dermatitis Medicamentosa

3. DEFINITION
• type of contact dermatitis
• Delayed cell-mediated HSN
• manifestation of an allergic response
• contact with an exogenous substance
• previous sensitization

4. EPIDEMIOLOGY
• 3700 documented allergens
• Children > Adults
• Females > Males ? Ni ? Fragnance Mix
• Males : 10-19 % Occupational (44% - Hand
Dermatitis)

5. ETIOPATHOGENESIS
• Type IV HSN
• T-cell mediated Inflammation to Haptens
• Genetic Susceptibility  HLA alleles to Co / Ni /
Cr
• Sensitization (Induction) – Elicitation –
Resolution
• Hapten + Epidermal Carrier Protein (LC) = Contact
Allergen
• Contact Allergen conjugate recognized by LC 
Presented to T-cells
• Internalized to LNs  LCs differentiate into DCs

6. PATHOGENESIS
• AA

7. CLINICAL FEATURES
• A

8. • ACUTE : pruritic papules and vesicles on an
erythematous base Erosions , crusting
• Edema in areas of higher absorption
coefficient – Mucosae / Eyelids / Genitals
• CHRONIC : Lichenified pruritic plaques ,
scaling
• Initial Site localization – causal

9. REGIONAL DISTRIBUTION

10. ACUTE ACD
10

11. ACUTE ACD
11

12. CHR ACD
12

13. VARIANTS
• Mucosae - Contact Aphthae / Lingual erosions /
Peri-anal dermatitis ; more in Geriatric group 
Poor hygeine , incontinence , mucosal dryness
• PARADOXICAL ACD
Weak allergens Contact / Damaged Epidermis
Gold on Metal Oxides
Paraben / Lanolin Eczema
Topical Corticosteroids

14. • Eythroderma / Exfoliative Dermatitis
• EM – Ni / Poison Ivy / Hair dye / Neomycin
• Non-Eczematous : Contact Purpura / Contact
Leucoderma / Lichenoid AC Reactions /
Erythema Dyschromia Perstans
• Allergic Contact Urticaria (ACU) – IgE ; Latex
Rubber / Colophony / Bacitracin

15. • Systemic Eczematization (Immunological
Memory + Secondary Systemic Exposure)
• ACD SYNDROME

16. DDx
• aa

17. DDx
• a

18. DIAGNOSIS
• DETAILED HISTORY
• CLINICAL EXAM / REGIONAL ALGORITHM
• PATCH TESTING +/- ROAT
• SPOT TESTS (DIMETHYLGLOXAMINE TEST)
• HISTOPATHOLOGY

19. PATCH TESTING (IN-VIVO)
• ISS (Indian Standard Series)
• TRUE (Thin-layer Rapid Use ; Epicutaneous)
• Other Series (Plant / Food / Vegetable /
Fragnance / Cosmetic / Textile)
‘Gold Standard’

20. INTERPRETATION
• − (0) Negative reaction
• ?+ Doubtful reaction; erythema only
• + (1+) Weak (nonvesicular) positive allergic
reaction; erythema, infiltration and possibly
papules
• ++ (2+) Strong (vesicular) positive allergic
reaction; erythema, infiltration, papules and
vesicles
• +++ (3+) Extreme positive allergic reaction;
bullous reaction
• IR Irritant reaction

22. PATCH TESTING (IN-VITRO)
• LEUKOCYTE TRANSFORMATION INHIBITION
• MACROPHAGE MIGRATION INHIBITION
• LYMPH NODE ASSAY

23. HPE
• Spongiosis
• Eosinophillic Folliculitis
• Microvesicle formation
• Perivascular infiltrate in
Dermis ; granuloma formation
noted

24. MANAGEMENT
• PHARMACOTHERAPY
– Aluminium Sulfate / Calcium Acetate
– Emollients
– Topical Antipruritic agents
– Antihistaminics
– Corticosteroids (topical / Oral)
– Calcineurin Inhibitors (topical / Oral)

25. PHOTOTHERAPY
P-UVA
NBUVB
PREVENTION
?? HYPOSENSITIZATION / TOLERANCE INDUCTION

26. THANK YOU