See the difference between science and Internet "noise": 114,000 search results for "Caffeine Allergy" from Google http://bit.ly/3JoV6U and zero from PubMed.
There is only one (1) obscure case report of "Anaphylaxis due to caffeine" from 2003 http://bit.ly/eEjYt
The classic Middleton's Allergy textbook mentions caffeine in the section for non-allergic adverse reactions to foods as a cause of tremors, cramps, diarrhea.
There is a similar Internet "pollution" when searching for "Chocolate Allergy" http://bit.ly/11fPke - a condition defined in the current guidelines for food allergy as "vanishingly rare" http://bit.ly/rbaZ4
More about dispelling Internet myths: contrary to popular belief, strawberry allergy is uncommon http://bit.ly/ecoCM
In conclusion, please be sure to receive your information about allergic diseases from allergists, other physicians and reputable sources.
Chocolate Allergy? It's Vanishingly Rare
Contrary to popular belief, strawberry allergy is uncommon
Food AllergyImage source: Wikipedia, public domain.