Gold standard for diagnosis of a food allergy or intolerance. The suspect food is strictly excluded for a period, generally not less than 2 weeks, and then the food is re-introduced. Symptom control during this process should confirm or refute the diagnosis. The challenge is only considered complete once a normal age-appropriate portion of the food has been consumed.

In certain cases, food challenge is potentially more dangerous, and should only be done in a specialist setting with emergency support immediately available, and if there is a moderate to high risk of a severe reaction, intensive care support should be immediately available:

• Where the initial reaction sounds severe (anaphylaxis or FPIES)
• Where the patient has asthma

The challenge can be blinded if there is still doubt. Objective measures of symptoms/signs may be required. Eczema, wheeze, congestion, diarrhoea should all have resolved prior to doing the challenge, to avoid potential confusion.

The risk of causing a reaction should be weighed against the potential benefit of removing dietary restrictions and reducing fear/anxiety.

[EAACI food allergy diagnosis, Allergy 2014]