Allergic disorders encompass skin, food and respiratory allergies. Sensitization to a normally harmless allergen results in the immune system being biased to a predominant T-helper type 2 response. Re-exposure to the same allergen leads to a robust secretion of allergy-related mediators that eventually triggers symptoms. Our understanding of these disorders has enabled the search of therapeutic approaches that can either modulate the sensitization process or impact on allergic mediators, thus helping manage allergic symptoms. Polyphenols are one such class of compounds that are found in foods and plant sources and have been investigated for their anti-allergic effect in different disease models and in human clinical trials. Their anti-inflammatory profile is known to impact on the recruitment of immune cells to the skin and in preventing the development of secondary infections following disruption of the skin barrier. The interaction of polyphenols with proteins can modulate the process of allergic sensitization and their direct effect on allergic effector cells such as mast cells inhibit mediator release, resulting in the alleviation of symptoms. In addition, their endogenous anti-oxidant ability limits the extent of cellular injury from free radicals during the allergic insult. Overall, polyphenols hold promise as anti-allergy agents capable of influencing multiple biological pathways and immune cell functions in the allergic immune response and deserve further investigation. The objective of the current review is to summarize the key findings and progress made in studying polyphenols as anti-allergic ingredients. Special emphasis is placed in this review to highlight key physiological, cellular and signalling pathways implicated in the mechanism of action of different polyphenols in the context of allergic disorders and their manifestations.

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BACKGROUND/OBJECTIVES: Probiotics are defined as 'living micro-organisms that when administered in adequate amounts confer a health benefit to the host'. Different probiotic strains have been investigated for beneficial effects on allergic disorders. The purpose of the current study was to evaluate the effect of orally administering the probiotic Nestlé culture collection (NCC)2818 Bifidobacterium lactis strain on immune parameters and nasal symptom scores in subjects suffering from seasonal allergic rhinitis (SAR). SUBJECTS/METHODS: The study was a double-blinded, parallel, randomized placebo-controlled trial conducted during the peak of the pollen season. Adult subjects with clinical history of SAR and positive skin prick test to grass pollen were recruited. The subjects received B. lactis NCC2818 or placebo for 8 weeks and completed symptom questionnaires every week. Whole blood was collected at baseline (V1), 4 weeks (V2) and 8 weeks (V3) to measure immune parameters. RESULTS: Concentrations of Th-2 cytokines, secreted by stimulated blood lymphocytes, were significantly lower in the probiotic group compared with the placebo group at V3 (interleukin (IL)-5, P ¼ 0.016; IL-13, P ¼ 0.005). Total nasal symptom scores were significantly lower in the second month of the study (weeks 5-8) in the probiotic group compared with the placebo group (P ¼ 0.03). Also, percentages of activated CD63 expressing basophils were significantly lower in the probiotic group at V2 (P ¼ 0.02). CONCLUSIONS: Oral administration of the probiotic NCC2818 mitigates immune parameters and allergic symptoms during seasonal exposure. These promising results warrant that B. lactis NCC2818 be investigated further in large-scale trials for management of respiratory allergy.

Polyphenol-enriched apple extract can attenuate food allergy symptoms in sensitized mice via two distinct possible mechanisms.