Correspondence (reply): In Reply

We thank our correspondents for their great interest in our study, and special thanks go to Dr Richter from the Federal Institute for Risk Assessment (Bundesinstitut für Risikobewertung) and Dr Hofmeister from the Consumer Centre of the German Federal State of Bavaria for their comments, which we are in complete agreement with. With regard to Dr Klehr’s letter, we have to admit that we do not have any data—neither from our own investigations nor from those of others—that confirm a special case for Merlot wines.

Real allergic reactions and/or other intolerance reactions can in principle be triggered by any ingredient within wine, but the likelihood varies. Such ingredients include substances used in the clarification and stabilization of wine and their known allergenic potential, such as mentioned in the letters from Dr Hofmeister and Dr Richter. In modern vinification processes these are hardly of any relevance, at least not in Rheinhessen, but they have had to be declared on the label since 2012 if they can be confirmed within the wine. Another class of factors that may trigger intolerance reactions include the phenols and phenolic flavonoids. Intolerance reactions are often reported for red wines, and their causes are not easily identifiable, especially if the wine is a blend of different grapes. We don’t think that any generalization is possible about whether Merlot is particularly important in this setting, as Dr Klehr remarks. As a rule, any reactions are person-specific and can be avoided only by not drinking wine and alcohol or changing to a wine that is more easily tolerated.

Of course acetaldehyde, a product of alcohol metabolism, also needs to be borne in mind, as this can trigger intolerance reactions.

Even though sulfite is used in winemaking since antiquity, in order to protect the wine against oxidation and micro-organisms, the well-known intolerance reaction and allergic reaction owing to sulfite needs to be mentioned in this context. Sulfite now has to be declared on the wine label. We are currently studying the molecular foundations for the interactions with different wine ingredients, in order to be able to better understand their effects on people’s health.

Dr Hofmeister rightly mentioned the Copenhagen study (1), which reported a similar prevalence of symptoms of intolerance after ingestion of alcohol, especially red wine, as our own study.