Quercetin a promising functional food additive against allergic Diseases: A comprehensive and mechanistic review

The crucial roles of innate and acquired immunity in the pathogenesis of allergic diseases have been well highlighted based on molecular mechanisms. Thus, the modulation of unregulated and unabated inflammatory responses is a therapeutic strategy in allergic diseases. One of the most important natural compounds with a high immune modulation and anti-inflammation potency is quercetin, found in various fruits and vegetables, namely onions, shallots, apples, and berry crops. Therefore, in this study, we reviewed the influences of quercetin against allergic conditions, including asthma, allergic rhinitis, atopic dermatitis, conjunctivitis, and anaphylaxis. Scientific databases, including PubMed, Scopus, the Web of Sciences, and EMBASE, were searched in English until March 2024. Quercetin's beneficial effects have been attributed to its anti-cancer, anti-viral, anti-oxidant, and anti-inflammatory activities, and also a decrease in pro-inflammatory cytokines, leukotrienes production, inhibition of histamine release, and suppression of interleukin IL-4 production. It can reduce the production of antigen-specific IgE antibodies and improve the Th1/Th2 balance. These qualities of quercetin can be used as a strategy to treat asthma, allergic rhinitis, atopic dermatitis, conjunctivitis, and anaphylaxis. According to the findings of these investigations, quercetin may have a beneficial influence on allergy illnesses.