Recent evidence has brought to the spotlight plant-derived polyphenols as a promising tool to prevent allergy. The worldwide increase of allergic disease, probably relying on many factors including immune response to stressors and its loss in complexity, environmental pressure by pollutants and chemical allergens, changes in lifestyle and lifespan, failure of conventional treatments to prevent and treat allergy, has strongly suggested people to refer to healthy promising nature-derived compounds, most of which contained in fruits and vegetables, e.g. in daily diet. Phenolic acids and polyphenols, such as flavonoids, are the best studied natural substances known to possess an anti-inflammatory and anti-allergic potential. Used as nutraceuticals, these compounds are thought to dampen the onset of allergic inflammation, by acting on several immune cells, but concerns still remain about their real employment by the organism who assumes polyphenols through diet, because of their bioavailability, gut transformation and pharmacokinetics. Other issues deal with the wide panoply of actions played by these compounds within cells, which has hampered a clear comprehension of their action on cell molecular signaling and function. In this review, special emphasis is placed on the effects of dietary polyphenols on allergy prevention, the possible mechanism of action of polyphenols-containing food and future perspectives for pharmacology design.