Sneezing, watery eyes, scratchy throat, runny nose – spring must be here! The good news is that long-lasting relief from the classic symptoms of seasonal allergic rhinitis can be found in a 100% natural nutritional substance called quercetin.
All fruits and vegetables contain a large group of compounds called polyphenols, certain of which – flavonoids – are the pigments responsible for the bright colours found in the plant kingdom. One is the flavonol quercetin, which is recognised as the most active of the flavonoid family. It is often combined with L-ascorbic acid, as it improves the latter’s effects in the body by increasing its absorption and delaying its elimination. Quercetin and vitamin C are mutually protective and regenerative.
Foods that provide reasonable amounts of quercetin include onions (15mg per 100g), apples (4mg per 100g), tea, red grapes and red wine, garlic, broccoli, red-purple berries, fresh dill, green and yellow beans.
Like all flavonoids, quercetin strengthens the small blood vessels, and has natural antioxidant and anti-inflammatory benefits through its effect on the metabolism of arachidonic acid, and thus prostaglandins and leucotrienes. In addition, it is particularly useful at this time of year because of its significant antihistamine, ie, anti-allergy, effects. Many studies have shown that quercetin is effective at stabilising the membranes of mast cells which are responsible for the release of histamine. By reducing degranulation of these cells, quercetin acts directly on the source of the allergic reactions and their associated symptoms.
However, it is necessary to take supplements, as well as consume a diet rich in quercetin, in order to obtain these anti-allergic and anti-inflammatory benefits.
Preliminary studies show that the isoquercitrine form (quercetin-3-glucoside) is more bioavailable to the body. Supplementing with isoquercetrin is thus particularly recommended for allergies, whether digestion-related or respiratory- such as asthma and hayfever, as well as for eczema and urticaria when combined with L-ascorbic acid and zinc.
As quercetin is primarily an effective preventive agent, supplementation should begin at least two weeks before the hayfever season and continue until the end of the season. It should be taken in the morning on an empty stomach or in between lunch or dinner, in doses of between 500 and 1000mg a day, spread over the day.
The absorption of dihydroquercetin or isoquercitrin can perfectly complement the use of allopathic antihistamine medication. In fact, studies have shown that individuals simultaneously taking conventional drugs and quercetin report a greater improvement in their symptoms.
Rainer Cermak et al., The bioavailibility of Quercetin depends on the glycoside moiety and on dietary factors in pigs, American Society fir Nutritional Sciences, 2003.
Thornhill SM, Kelly AM. Natural treatment of perennial allergic rhinitis. Altern Med Rev. 2000;5(5):448-454.
Otsuka H, Inaba M, Fujikura T, Kunitomo M. Histochemical and func¬tional characteristics of metachromic cells in the nasal epithelium in allergic rhinitis: studies of nasal scrapings and their dispersed cells. J Allergy Clin Immunol. 1995;96:528-536.
Chang Q, Zuo Z, Chow MS, Ho WK. Difference in absorption of the two structurally similar flavonoid glycosides, hyperoside and isoquercitrin, in rats. Eur J Pharm Biopharm. 2005;59(3):549-555.