Allergic reactions to red meat are relatively uncommon and responsible for approximately 3% of all food allergies. 1 Recently, a new syndrome has been described in which delayed onset of anaphylaxis occurs 3 to 6 hours after mammalian meat consumption. This reaction is associated with IgE antibodies directed against oligosaccharides galactose-alpha-1,3-galactose (alpha-gal). 2 Following this finding it was concluded that some patients previously diagnosed with “spontaneous” or “idiopathic” anaphylaxis may have had delayed anaphylaxis to red meat that was not immediately recognized because of the significant delay between the exposure to meat and the appearance of symptoms. 3 Although avoidance is the main treatment option for food allergies, it can cause difficulties especially in children who are allergic to common foods. 4,5 For that reason, food immunotherapy trials have been undertaken with children to selected foods, such as milk and peanuts. 6 Since the avoidance of beef or lamb is not difficult for adults, desensitization has not been commonly considered as an option for “red meat” cases.7 Here, we present 2 cases of delayed-onset red meat allergy that were successfully desensitized to beef.
Full Paper - http://dx.doi.org/10.1016/j.jaip.2016.12.008
Basically this is the tick based alpha-gal allergy that has recently made waves in the news. 2 People have been re-sensitized to red meat over a month.
Others have self reported being on carnivore and self-clearing the allergy following a similar protocol https://carnivore.diet/allison-cleared-alpha-gal-symptoms-on-a-carnivore-diet/
TLDR - Early stages of knowledge building around this tick borne allergy, but it's not the end of carnivore.
Of course a carnivore can continue to eat fish and poultry even with a alpha-gal sensitivity
The Meat of the Matter: Understanding and Managing Alpha-Gal Syndrome
Great overview article.
A carnivore could eat fish and birds, but getting desensitised is valuable as ruminant meat is by far the best food