Antiallergic activities of shallot (Allium ascalonicum L.) and its therapeutic effects in allergic rhinitis.

Abstract

Onion has antiallergic activity but lack of evidence for shallot. To determine whether shallot owns similar antiallergic activity to onion and its therapeutic effects in allergic rhinitis when added to standard treatment. In-vitro β-hexosaminidase inhibitory activities of shallot was compared with onion on RBL-2H3 cells. In clinical study, a randomized, double-blind, placebo-controlled trial was performed. Sixteen AR patients were randomized equally into the controls who received cetirizine 10 mg once daily and placebo capsules for 4 weeks, and the treatment who received 3g of oral shallot per day (equivalent to 1 ½ bulbs) and cetirizine. Visual analog scores of overall symptoms (VAS), total nasal and ocular symptom scores (TNSS and TOSS), nasal airway resistance (NAR), and adverse events were assessed. Shallot extract at 200 μg/mL had an average β-hexosaminidase inhibition rate of 97% while onion extract had 73%. HPLC chromatograms (λ = 290nm) of both plants showed nearly identical patterns of quercetin compounds, such as quercetin 3,4'-diglucoside, quercetin 4'-glucoside, and quercetin. After 4-week of treatment, 62.5% of patients in shallot group and 37.5% of patients in control group showed improvement of post-treatment VAS. TNSS were significantly reduced in both groups, however no difference between groups (P = 0.18). TOSS were significantly improved only in the shallot group (P = 0.01). Adverse events from shallot were not different from placebo. Shallot had antiallergic activity and similar quercetin compounds to onion. The shallot oral supplement and cetirizine was shown to improve the overall AR symptoms more than cetirizine alone.