About 20 years ago my find discovered that she was allergic to 'red dyes'. Red dyes, most commonly used as a 'color enhancer in foods and medicines' include, but are not limited to, Red #4,Red #3,Red #40 and Red #33. There are similar allergies to the various 'yellow dies' used in foods and medicines for the same reasons.
She normally pays EXTREMELY close attention to the ingredients of things she uses and consumes. On more than one occasion she has had to refuse prescription medications due to the inclusion of such dies. 'Yes', her allergy IS listed in her medical records and is on file with local pharmacies. HOWEVER, it has become dangerously apparent that doctors and pharmacists DO NOT read said files.
This past Thursday we were shopping in the local mall. We ended up in a local 'supplement store' pondering their wares. For whatever reason, the salesman (he was GOOD!) convinced us to buy daily supplements (in the little daily multi-packs). We failed to VERIFY that NO RED DYES were present in ANY of the supplements. We DID mention her allergy to the salesman, though.
She spent the next afternoon in a local ER. Her eyes had swollen shut and she was having difficulty breathing. Even today, she is still feeling the effects of the dye, which turned out to be 'Red 40'.
FWIW, most artificial dyes are 'petroleum based', or are a member of the 'iron oxide' family. WHY the FDA allows such 'ingredients' in foods and medicines is beyond me, especially when 'beet juice' can serve the same purpose. To my knowledge, NO 'beet allergies' have been reported.