Taurine is one of the most abundant free amino acids in all mammalian tissue, and it is not an amino acid in the usual meaning as a component of protein, called an amino acid in the meaning of an acid containing amino group [4
]. Taurine is mainly biosynthesized from cysteine in the liver, known to have many important roles such as conjugation of bile acids, antioxidation, osmoregulation, detoxification, membrane stabilization and modulation of calcium reflux [4
]. Also, it contributes to cardiovascular function, and development and function of skeletal muscle, retina and central nervous system [7
Taurine presents naturally in food, especially in meat and seafood. Although the mean daily intake from diet was reported to be less than 400 mg/day in several studies [8
], the European Food Safety Authority reported that up to 1,000 mg/kg/day of taurine have no adverse effects. In Korea, popular energy drinks generally contain 2,000 mg taurine in one bottle (100 mL). Most energy drinks sold in worldwide contain 1,000 mg taurine. By literature searching, there is no available data about toxicity or hypersensitivity of taurine in human. Only a few studies reported that excess dosage of taurine led to haemosiderine deposition in the lung [10
] or fatty infiltration of the live [11
] on animal experiments.
Our patients showed hypersensitivity reaction with synthetic taurine, but in the test of natural taurine, she had no symptom. We could not find other case of anaphyalxis to synthetic amino acid. There are just a few reports on anaphylaxis caused by compound amino acid solutions. Although the authors could not elucidate the mechanism of anaphylaxis, they suggested the additives for stabilization of amino acid like sulfites, butylates hydroxyanisole, butylated hydroxytoluene, polysorbate emulsifier could be the cause of symptoms [12
]. As an example of difference in synthetic and natural materials, Smith et al. [14
] reported a case of recurrent anaphylaxis only to synthetic folic acid, but not to dietary folates. They postulated that synthetic folic acid acted as a hapten with different mechanism from dietary folates. Although taurine is only small molecular weight of amino acid, not a peptide, it seems that only synthetic taurine is intolerable to our patient by unknown mechanism. Our patient showed positive responses in oral challenge test with synthetic taurine-containing drinks and synthetic taurine, but skin prick test and basophil activation test with synthetic taurine were negative. Most synthetic taurine used in the food products and drinks are prepared by amination at elevated pressure of isothionic acid salt from ethylene oxide and sodium hydrosulfite [15
]. Synthetic taurine might be slightly different from original natural taurine through its industrial processing and some hidden materials happened to be contained within it. However, as far as we know, synthetic taurine is not different from natural taurine in its molecular structure, and the purity of synthetic taurine we used was nearly 100%.
Hence we postulated that anaphylaxis in this patient was caused by non-immunologic mechanism or by haptenization. Recently, as the consumption of energy drinks increase, the safety of ingredients of energy drinks has been of concern worldwide. We hereby reported the first case of taurine-containing drinks induced anaphylaxis, especially by synthetic taurine.