Background Patch test is the gold standard for diagnosing allergic contact dermatitis. Conventionally, the patches are applied for 48 h, which in tropical weather conditions causes excessive sweating, leading to irritation, and sometimes the patches come off, making the test inconclusive. Objective To compare the patch test positivity after 24 and 48 h of occlusion time in patients of allergic contact dermatitis, using standard allergen concentration. Materials and methods Clinically suspected patients of allergic contact dermatitis were enrolled and patch tested using the Indian Standard Series, parthenium acetone extracts (1:50, 1:100 and 1:200 dilutions) and patient material. Patches were applied in duplicate on either side of the back, using a random number table. One set of patches was removed after 24‐h of occlusion, while the other set after 48‐h. Readings were performed at 48‐ and 96‐h by two independent dermatologists, blinded to the duration of occlusion. Results The study had 97 adult patients (58 males and 39 females; mean age: 48.12 ± 13.07 years). A total of 133 and 142 positive reactions were observed after 48 h occlusion at 48 and 96 h reading, respectively. Of these 117 (87.9%) and 132 (92.9%) patches were positive and concordant and noted at 24 h occlusion time. The Cohen's kappa coefficient were 0.94 for 48 h and 0.97 for 96 h reading, hence showing an almost complete agreement (ⱪ > 0.81) between patches occluded for 24 and 48 h. Conclusion Though there is no significant difference in patch test positivity among ISS allergens after either occlusion time, 48 h occlusion performs significantly better compared with 24 h, when reactions of all allergens (ISS, patient material and parthenium acetone extract) are analysed together. Our study compares patch test positivity in 97 patients of allergic contact dermatitis after 24 and 48 h of application. Using standard allergen concentrations, we found no significant difference in Indian Standard Series allergens. However, when analysing all allergens together, 48 h application outperformed 24 h. Moreover, positive reactions after 48 h had increased severity (grading) as compared with after 24 h. Our results suggest that a shorter occlusion time may be sufficient, enhancing patient comfort and test reliability, particularly in tropical climates. Consideration for a new standard occlusion time is proposed, with further multicentre studies needed for validation.