Most people with food allergies are allergic to one or few foods, but allergies to more than three foods are relatively rare (PubMed, 2010). In some people who are allergic to several foods, an underlying condition is discovered, for example:
Question: Are there other known conditions that are associated with food allergies and are there any known triggers that trigger their onset?
To put the questions in the context: Does it make sense for someone with (multiple) food allergies to undergo investigations to find an eventual underlying disorder or trigger? Because, sometimes, treatment with desensitization may be possible.
The focus of the question is not on "multiple," but I was thinking it is more likely that multiple allergies have known underlying causes. So, I'm looking for a list of "underlying conditions," "related conditions," "risk factors" and "triggers" of food allergies.