Carboplatin, a second-generation platinum compound, is a chemotherapeutic drug effective in many types of cancers. Its use is limited by the development of systemic allergic reactions in up to 30% of the cancer patients. Therefore, it is very important to make a correct diagnosis of true carboplatin allergy, for the crucial clinical implications. In this regard, no biological test is actually available to detect specific immunoglobulin E in the sera of patients allergic to carboplatin. We evaluated a new experimental biological test in patients with suspected immunoglobulin E-mediated reactions to carboplatin. Three patients with suspected hypersensitivity reactions to carboplatin underwent skin tests with an undiluted aliquot (10 mg/ml) of carboplatin preparation planned for infusion. Total serum immunoglobulin E and specific immunoglobulin E to the two platinum salts carboplatin and cisplatin were determined with the ImmunoCAP system (Phadia AB, Uppsala, Sweden). We detected specific immunoglobulin E to carboplatin in all three patients, whereas specific immunoglobulin E to cisplatin was observed in one patient. The positivity of specific immunoglobulin E against carboplatin in these three patients is a new and encouraging observation for the development of a new important instrument that can help clinicians in their therapeutic decisions, after a hypersensitivity reaction to a platinum salt.