Bronchodilator reversibility (BDR) testing is a vital tool in the objective diagnosis of paediatric asthma, as per current BTS, NICE, and SIGN guidelines. Salbutamol, a short-acting beta2 agonist (SABA), is typically used. However, we present a clinical case where Formoterol Fumarate, a fast-acting long-acting beta agonist (LABA), was successfully employed for BDR testing in a child with intolerance to Salbutamol. To our knowledge this is first case report of a 10 years old child where Budesonide/Formoterol was used for BDR. A 9% improvement in FEV1 was observed following the use of Symbicort Turbohaler® (Budesonide/Formoterol), closely approaching the 10% threshold for positive reversibility. Although evidence in children is limited, our case supports the consideration of Formoterol in select scenarios, particularly when adverse reactions to SABA therapies limit diagnostic assessment and also for those children who are on exclusively Budesonide/Formoterol (MART or AIR therapy).