Side effects during allergen desensitisation are common. These are mainly mild to moderate (localised itching, acute angioedema, urticaria, abdominal pain) but a significant number of individuals experience acute anaphylaxis or long term gastrointestinal dysfunction (eosinophilic oesophagitis). Anaphylaxis appears more common in those having previously experienced an anaphylactic reaction to the food. Moreover, acute reactions can be precipitated in individuals whose threshold has been reduced by viral infections, menses, exercise, sleep deprivation and NSAID use. All children undertaking food immunotherapy must be prescribed adrenaline auto-injectors and be trained in their use.