Role of Patch Testing in Chronic Spontaneous Urticaria.

Background Chronic spontaneous urticaria (CSU) is a common debilitating condition. Although not completely understood, the main pathomechanism involves autoimmune-related mast-cell degranulation. Patch test (PT) is the gold standard for the diagnosis of type IV cutaneous hypersensitivity. The relevance of PT to the diagnosis of CSU is debatable. Objective We aimed at determining the role of PT in selected patients with CSU. Methods In this retrospective study, we reviewed cases of patients referred for patch testing at our clinic. We compared results of patients with CSU (n = 134) and patients with suspected allergic contact dermatitis (n = 680; control group). Results Among patients in the CSU group, 3% of patients had relevant reactions to PT, indicating that contact allergen avoidance resulted in resolution of all skin findings. Metals and textile dyes were the most relevant allergens. No significant differences were found between the groups with regard to the percentage of patients with positive PT and hapten reaction profiles. Patients from the CSU group were significantly older (4.1 years on average, P < 0.05), consisted of more females, and were less likely to have atopic trait (46% vs 58%, P<0.05). Conclusion In some of patients, PT may assist in determining the cause of CSU.