Dr Tom Marrs is Consultant Paediatrician specialising in Allergy and Clinical Immunology, with two decades of experience in the treatment of children's allergies. Dr Marrs is Chair of the Paediatric Allergy Committee for the British Society of Allergy and Clinical Immunology (BSACI). He leads the Allergy Prevention Service at Guy's and St. Thomas' Hospital and the Joint Allergy-Gastroenterology Service at Evelina London. He led the Scientific Programme for the BSACI Conference from 2018-2020. Dr Marrs sees private patients at OneWelbeck Marylebone, next to Bond Street, north of Oxford Street.

Dr Marrs graduated from Clare College, Cambridge University, in Medicine, Medical Ethics and Law. He completed his primary medical qualification in 2003 from St Barts and the Royal London Hospital, after taking specialist study at the Astrid Lindgren's Children's Hospital, Karolinska Hospital, as well as studying in Sri Lanka and Nepal. Dr Marrs then undertook his specialist paediatrics training at various renowned London hospitals including the Royal Brompton, Great Ormond Street and Guy's Hospital. Since completing his training, Dr Marrs was awarded his PhD in eczema, food allergy and the prevention of food allergies, and has been appointed Director of the Allergy Academy, King's College London, where he is also a Senior Honorary Lecturer with Adjunct.