A 22-year-old medical student develops erythematous, vesicular, intensely pruritic lesions on both hands 24 hours after wearing latex gloves for a surgical posting. Patch testing is planned. Which of the following is the CORRECT reading time for a standard patch test to detect Type IV (delayed-type) hypersensitivity?
- A 15–20 minutes after application
- B 1–4 hours after application
- C 7–10 days after application
- D 48–96 hours after application ✓
Explanation
Allergic contact dermatitis is a Type IV (cell-mediated/delayed-type) hypersensitivity reaction. The standard patch test (Finn chamber or IQ chamber method) is read at 48 hours (when the chambers are removed) and again at 72–96 hours to detect delayed reactions and differentiate true positives from irritant responses. Reading at 15–20 minutes detects immediate (Type I) IgE-mediated reactions in prick/intradermal tests. This student's occupational latex dermatitis warrants patch testing with the ICDRG (International Contact Dermatitis Research Group) standard series.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.