Authors' reply

Chembolli Lakshmi, CR Srinivas

 Dept. of Dermatology, PSG Hospitals, Peelamedu, Coimbatore - 4, India

Correspondence Address:
C R Srinivas
Dept. of Dermatology, PSG Hospitals, Peelamedu, Coimbatore - 641 004
India

Sir,

We thank Dr. Kaushal Verma for his interest in our article. ^[1] The author of the letter states, ′Atopics are more susceptible to develop contact allergy to compositae plants also. In this study, it seems atopic individuals have developed Parthenium dermatitis and this atopic state may have resulted in positive prick test and elevated IgE levels in these patients . . .′ Until this point, we concur with the authors of the letter; however, the authors continue, ′. . . which may not have been actually due to parthenium.′

These patients tested positive to prick test with parthenium and negative with saline (negative control). In addition, histamine, which was used as a positive control, also elicited an immediate reaction. The late-phase reaction (LPR) was elicited to parthenium alone and neither the control nor histamine showed a late-phase reaction. This proves that the patient had type I hypersensitivity in addition to type IV hypersensitivity (which was confirmed by patch testing). With regard to the comment that ELISA would be a more reliable test to confirm type I hypersensitivity to parthenium, the only available test is RAST. During our initial trials, RAST gave false positive results. A 6-month-old baby with pustular psoriasis tested positive, and some frank cases of parthenium dermatitis tested negative. In addition, the RAST yields numerous positive reactions which are obviously irrelevant and poses a problem in advising patients. Finally, we planned our study based on an article in Dermatology Clinics which categorically states ′the RAST is considered to be less sensitive than a prick test.′ ^[2]

1.	Verma KK. Type I hypersensitivity to Parthenium hysterophorus in patients with parthenium dermatitis. Indian J Dermatol Venereol Leprol 2007;73:(in current issue). [Google Scholar]
2.	Warner MR, Taylor JS, Leow YH. Agents causing contact urticaria. Clin Dermatol 1997;15:623-35. [Google Scholar]