The cornerstone of food allergy diagnosis is the clinical history. The taking of a complete history of the reactions is vital and must include the reported symptoms, speed of onset and suspected trigger foods as well as co factors (see below). To base a diagnosis on tests alone could result in foods being avoided needlessly or conversely the real trigger may not be identified and therefore can cause reactions in the future. The following publications have more details regarding key questions to ask when taking a history. (link to Nice guidelines and also diet history paper). The history is also a good indicator of the likelihood of an IgE-mediated food allergy. In children, delayed onset symptoms or those of a more gastro-intestinal nature may indicate a non-IgE mediated food allergy such as protocolitis, FPIES and Eosinophilic Oesophagitis. In adults, reported symptoms to many different and seemingly unconnected foods can still indicate an IgE-mediated food allergy but may also suggest a sensitivity to naturally occurring substances in foods such as vaso-active amines or to food additives.
