AKT-0012

A 5-year-old boy is brought by his mother to the Out-of-hours (OOH) walk-in centre. She reports that he is thought to have an allergy to peanuts and is waiting for an Allergy Clinic outpatient appointment. He has eaten a piece of birthday cake at a party about 30 minutes ago and has quickly developed facial flushing, with swelling of the lips and face. He has become wheezy and is now unable to talk in complete sentences.
What is the most appropriate management option?