You joke but… in tech school cantine, there was this “Vitamine Well” drink i took, since it was the only one that’s not too acidic (easily get heartburn). I had fissures in the corner of the mouth for years there and then it was suddenly gone. Later, i read that deficiency in some vitamin B variations (which were in that drink) causes said fissures. Since then i buy it once all one or two weeks and have no fissures anymore.

Long story short; they’re not entirely useless.