Allergic rhinitis, commonly known as hay fever, is a noninfectious inflammatory condition characterized by elevated levels of immunoglobulin E (IgE), nasal congestion, and other related symptoms after exposure to an allergen. Atopic dermatitis is an inflammatory skin disease mediated by T cells. It has a higher prevalence in pediatric populations (up to 20% of children) as compared to adults. Allergic rhinitis and atopic dermatitis are risk factors for the development of allergic asthma. The onset of asthma often occurs during childhood. Asthma, allergic rhinitis, and atopic dermatitis are frequently associated together, as they comprise the atopic triad.
Allergic illnesses are often associated with immune responses that include a shift to the T helper type (Th)2 phenotype in the Th1/Th2 balance. Th2 cells can produce cytokines such as interleukin (IL)-4, Il-5, and IL-13, which can influence the inflammatory response in allergic asthma. Mast cell recruitment increases in allergic asthma, along with IgE and mucus production. Studies indicate that quercetin may help support the allergic response.
Quercetin is a molecule found abundantly in onions, apples, green tea, and other fruits and vegetables. It has been shown in studies to support antioxidative status, neuroinflammation, and the elimination of senescent cells. Quercetin is classified as a polyphenolic flavonoid and has many biochemical actions, including the activation of sirtuin 1 (SIRT1). SIRT1 is involved in the modulation of cellular senescence and reactive oxygen species.
Quercetin may also help support a healthy inflammatory response. It has been shown in studies to help regulate SIRT1 pathways involving nuclear factor-kappa B and nuclear factor erythroid 2-related factor 2 (Nrf2). Quercetin administration has also been shown to help modulate inflammatory cytokines, including IL-1β, IL-6, and tumor necrosis factor.
A study involving animal models of allergic asthma indicated that quercetin administration helped support normal tracheal contractility. A laboratory study assessing the efficacy of a combination of polyphenols, including quercetin showed ciliary beat frequency improvements in human nasal mucosa. Other laboratory studies have shown that quercetin may help improve airway epithelial cells through the regulation of the signal transduction pathway protein kinase C and epidermal growth factor receptor extracellular-regulated kinase. Significant decreases in histamine levels and improvements in mucus hypersecretion and Th1/Th2 balance have also been observed in animal and laboratory studies related to quercetin.
Quercetin may also help support health in the presence of atopic dermatitis and allergic rhinitis. A laboratory study showed quercetin helped modulate nitric oxide production from nasal epithelial cells after IL-4 stimulation. Weaker expressions of cyclooxygenase-2 and vasoactive intestinal polypeptide were reported in a controlled animal study related to allergic rhinitis. In animal models related to atopic dermatitis, quercetin was observed to help suppress Th2-related cytokine expression. Quercetin helped suppress hyperkeratosis, parakeratosis, acanthosis, and mast cell activity in another atopic dermatitis animal model.
Before conclusions can be made, further studies need to be conducted in a clinical setting, particularly those with more participants and a pediatric lens. However, research indicates that quercetin may support antioxidative status and certain qualities of the allergic response.
By Colleen Ambrose, ND, MAT