There has been little sociological research on food allergy in North America, despite the fact that it impacts a significant population in the US and Canada. Immunotherapy for food allergy is now a prominent area of investigation and experts argue it is one dimension of a ‘paradigm shift’ that encourages exposure to food allergens in contrast to avoidance of them. This article reports on an ethnographic investigation of immunotherapy for food allergy research and practice between the years 2015 and 2020. I report on analyses of N = 31 in-depth interviews with spokespersons with different types of engagement in immunotherapy and over 100 h of ethnographic observations at clinical and scientific conferences. My research revealed the entangled ontologies of food and drug in immunotherapy and related uncertainties in the diagnoses of food allergy, which catalysed further uncertainty about who is receiving and who should receive immunotherapy (IT). Relatedly, there are uncertainties about the goals and/or outcomes of IT. I elaborate on previous sociological work about how uncertainty is valued in medicine and science. I argue shared uncertainties and mutual scepticism in IT co-exist, representing a passive (productive) tolerance and reticently accepted form of tension in the domain, which have resulted in calls for intra-professional and inter-professional collaborations and the involvement of other stakeholders in knowledge making regarding food allergy immunotherapy.