Prick testing in chronic idiopathic urticaria: A report from a tertiary care centre in south India

Abstract

Background: Chronic idiopathic urticaria can be provoked by a number of known and unknown factors and allergens. Some of these allergens can be identified by prick tests. Objectives: To determine the frequency of chronic idiopathic urticaria and to identify the antigens showing positive reactions to skin prick test. Patients and Methods: Fifty patients with chronic idiopathic urticaria were screened from patients attending Skin department of our institute and they were evaluated by prick testing. Results: The mean age of the patients was 33 years. Female to male ratio was 4:1. On skin prick test, 22 patients (44%) had positive response to one or more antigens – 9 patients had positive reaction to single antigens, and 13 patients had positive reaction to more than one antigen. Insects and pollens showed maximum number of positive reactions (12 cases each, 24%), followed by food items (11 cases, 22%), animal danders (7 cases, 14%), house dust mite (6 cases, 12%) and moulds and yeasts (5 cases, 10%). Five most common antigens to show positive reactions in our study were (in descending order of frequency): cockroach (7), house dust mite (6), cat danders (6), housefly (5) and rice grain dust (4). Positive skin prick test reactions were not significantly influenced by age, gender, and duration of the disease. Conclusions: A notable proportion of cases with chronic idiopathic urticaria demonstrate sensitivity to cockroach, house dust mites, pollens and animal danders. Thus, skin prick test is an important diagnostic procedure in such cases, where all other investigations have been fruitless.