As the most valuable beer brand in the world, Corona is a familiar name. Associated with beach time fun and backyard barbecues, the Mexican lager is often accompanied by its trusty sidekick, a fresh green lime wedge hanging off the top of the bottle. There are several versions of the origin story for this classic pairing, and it’s anybody’s guess which one is actually true.

Some say that the metal caps used to seal bottles of Corona are notorious for leaving rust marks on the rim and that the lime acts as a rust-remover and sterilizer. A similar principle applies to the claim that the citrus works as a disinfectant, which makes sense considering that the drinking water in Mexico is known for its deleterious effects on health. At odds with these claims is the fact that Corona has been brewed for over a century, and locals were never known to add lime before recent times.

Others suggest that Corona’s clear bottles leave the brew prone to a skunky flavor and aroma — as exposure to light causes the bitter alpha acids in beer to transform into the same chemical contained in a skunk’s spray — and that the fragrance of lime juice helps mask this odor. It has also been said that the lime is meant to keep flies out of the beer, as citrus is a natural bug repellent.

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Arguably the most likely scenario is the claim that a bartender started the trend in 1981 to increase the marketability of the Mexican lager.

While scant evidence exists to back up any of the claims, it is likely that a combination of factors led to the pairing’s prolonged popularity.

The brand has noticeably embraced the act, as practically every advertisement includes citrus of some sort — and in 2017, Corona became the official sponsor of the University of Texas Longhorns with the launch of its “Horns Up, Limes In!” campaign. It even flirted with a lime distribution partnership in 2018, releasing branded fruit in collaboration with Earth Source Trading.

While nobody is quite sure when or why the tradition began, it’s now hard to imagine drinking a cold Corona without  lime.