An allergic reaction during the caesarean section can be harmful for mother and foetus. Our patient has undergone an urgent caesarean section due to the imminent threat of foetal hypoxia. After operation, we applied prolonged mechanical ventilation. The anaesthesia was induced with thiopental and suxamethonium. Suxamethonium is associated with the highest incidence of allergic reactions but it is a neuromuscular blocking agent of choice for an emergency operation. During the operation, about 10 min. after induction, the systolic blood pressure dropped suddenly to 67 mmHg, the heart rate increased to 145 beats per minute and the oxygen saturation dropped to 60 %. A small degree of bronchospasm developed but there wasn’t any kind of skin reaction. We thought of an allergic reaction, the obstetrical pulmonary embolism and an acute cardiac failure. The baby was delivered promptly in good condition. Within 10 min. all vital signs normalized. The operation continued without problems. Unexpectedly, during waking up from anaesthesia the patient became dyspnoeic, laryngospasm appeared, the oxygen saturation dropped again, strong facial and tongue oedema appeared and an urgent reintubation had to be performed. The laboratory results pointed out elevated mast cell tryptase level and significant pseudocholinesterase deficiency. About 2 months later, immunologist excluded thiopental and latex, and suggested that suxamethonium was the “trigger” factor. In our case the respiratory insufficiency was caused by two different and unrelated pathological mechanisms: biphasic allergic reaction and prolonged neuromuscular block caused by pseudocholinesterase deficiency.