Comparison of contact sensitivity in patch test with the aqueous and acetone extracts of Parthenium hysterophorus

Objective: To compare the frequency of patch test positivity to Parthenium hysterophorus by using aqueous and acetone extracts of fresh plant in patients of allergic contact dermatitis (ACD). Patients and methods: 115 clinically diagnosed patients of allergic contact dermatitis involving ≥40% of body area were enrolled from dermatology outdoor department. After taking informed consent patch test was performed with aqueous and acetone extracts of fresh plant. Aqueous allergen was prepared in three serial dilutions as 0.1%,1%, and 10% strength. 1% acetone extract allergen was taken as gold standard for comparison as well as positive control while pure aqua was taken as negative control. Patch test results were interpreted according to ICDRG criteria Results: 115 patients of ACD consisted of 88 males and 27 females with the age range of 20 to 75 years (mean 42±10.20 years). Patch test showed positive contact sensitivity in 56 (49%) patients with 1% acetone extract, in 52 (45%) patients with 10% aqueous extract, in 44 (38%) patients with 1% aqueous extract and in 13 (11.3%) patients with 0.1% aqueous extract. Irritant reaction was seen in 20 (17%) patients with 1% acetone extract, in 12 (10%) patients with 10% aqueous extract and in 5 (4%) patients with 1% aqueous extract. Conclusion: Contact sensitivity to P. hysterophorus can be diagnosed with patch test by applying either aqueous or acetone extracts of fresh plant. Aqueous extract is safe (as it produced less number of irritant reactions) and almost equally sensitive allergen. Thus it can be a readily available alternate allergen for patch test in diagnosing parthenium sensitivity.