Non-IgE mediated cow's milk allergy is a broad term encompassing multiple clinical presentations and wide range of severity with differing prognoses. On the severe end of the spectrum is food-protein induced enterocolitis syndrome (FPIES). I would recommend the article referenced below by Nowak-Wegrzyn et al. which provides detailed recommendations on diagnosis and management of FPIES. To briefly address your questions, anaphylaxis does not occur with FPIES, although there are a subset of children with FPIES who can have specific IgE to cow's milk. This has been associated with more prolonged disease course. Further, with prolonged avoidance, it is possible for a child such as this to have anaphylaxis on re-exposure. In terms of challenges for FPIES, the document below recommends that children with prior severe reactions should be challenged in a location capable of providing IV-fluid rehydration. Location of challenges of children with histories of mild-moderate FPIES reactions should be made with shared-decision making between the provider and family.
Nowak-Wegrzyn A, Chehade M, Groetch ME, Spergel JM, Wood RA, Allen K, Atkins D, Bahna S, Barad AV, Berin C, Brown Whitehorn T, Burks AW, Caubet JC, Cianferoni A, Conte M, Davis C, Fiocchi A, Grimshaw K, Gupta R, Hofmeister B, Hwang JB, Katz Y, Konstantinou GN, Leonard SA, Lightdale J, McGhee S, Mehr S, Sopo SM, Monti G, Muraro A, Noel SK, Nomura I, Noone S, Sampson HA, Schultz F, Sicherer SH, Thompson CC, Turner PJ, Venter C, Westcott-Chavez AA, Greenhawt M. International consensus guidelines for the diagnosis and management of food protein-induced enterocolitis syndrome: Executive summary-Workgroup Report of the Adverse Reactions to Foods Committee, American Academy of Allergy, Asthma & Immunology. J Allergy Clin Immunol. 2017;139(4):1111-26 e4. Epub 2017/02/09. doi: 10.1016/j.jaci.2016.12.966. PubMed PMID: 28167094.
Hope this is helpful.
Daniel J. Jackson, MD, FAAAAI