The mystery of 'red wine headaches' has been solved by scientists.
Experts have long been stumped as to how drinking red wine can bring on a sore head in less than 30 minutes but researchers at the University of California now suggest that a naturally occurring compound is to blame.
The substance, called quercetin, is otherwise healthy but disrupts a person's ability to break down alcohol when combined with red wine - prompting migraines, flushes and nausea.
Professor emeritus Andrew Waterhouse, from the university's viticulture and ecology department, said: "When it gets in your bloodstream, your body converts it to a different form called quercetin glucuronide.
"In that form, it blocks the metabolism of alcohol."
The team noted that not all red wines have the same effect with sunlight, age and the wine-making process all influencing whether a glass can bring on a headache.
Wines from sunnier climates are more likely to have a higher quantity of quercetin and therefore trigger an immediate sore head.