Fresh onion juice is a traditional remedy that dermatologists have recommended for cutaneous inflammatory response to bee and wasp stings. Onions have shown the ability to inhibit inflammatory responses and participate in the resolution of inflammation. Quercetin is a plant pigment and flavonoid found in many fruits and vegetables. Onions are high in quercetin: Red and yellow onions contain the most quercetin, with red onions containing 39 mg per 100 grams. Quercetin has important biological properties, anti-inflammatory, antihistamine, and anti-oxidative actions (1).
Cutaneous, nasal, and bronchial allergen challenges of allergic patients are often followed not only by immediate but also by late immune responses. These late reactions start 2 hours after the allergen challenge and last up to 36 hours. It is well-established that immunoglobulin E (Ig-E) and anti-Ig E antibodies are capable of inducing late cutaneous reactions (1).
In a double-blind study, alcohol/onion extract (5% ethanol) was injected simultaneously with 20 IU and 200 IU rabbit anti-human-Ig E intradermally in 12 adult volunteers (6 atopics, 6 non-atopics). Diameters of wheals and flares were measured 10 min after and compared with control sites challenged with 20 IU and 200 IU anti-Ig E in a 5% ethanol solution. The skin sites were then treated epidermally with 45% alcohol/onion extract and 45% ethanol under occlusion. Diameters of late cutaneous reactions were measured hourly. Oedema formation was clinically estimated using an arbitrary scale and skin thickness was measured with a caliper (1).
In the onion-treated skin sites, the wheal areas were significantly reduced (at the 20 IU low dose: control: 108 ± 53 mm2; onion 69 ± 42 mm2, p< 0.05; at 200 IU anti-IgE the high dose: control: 152 ± 25 mm2, onion: 138 ± 26 mm2, p< 0.02). During the late phase skin reaction, the oedema formation was markedly depressed (p < 0.005 at 2 hours, p < 0.01 at 4 and 6 hours, p < 0.02 at 8 hours). The extent of late skin reactions was slightly, but not significantly reduced. These results suggested that onions contain pharmacologically active substances with anti-inflammatory and anti-allergic properties (1).
One study examined whether shallot (a smaller and sweeter variety of onion) has similar antiallergic activity to onion and its therapeutic effects in allergic rhinitis. They first compared the β-hexosaminidase inhibition rates of type I allergy in Rat Basophilic Leukemia cell line between shallot and onion. After the antiallergic activity of shallot had been confirmed in the cell-culture study, a randomized, double-blind, placebo-controlled trial was performed in allergic rhinitis patients. This study aimed to determine whether shallot has antiallergic properties similar to onion and benefits the allergic treatment when combined with cetirizine (a standard treatment medicine) for allergic rhinitis patients (2).
Sixteen allergic rhinitis patients were randomized either into the controls who received cetirizine 10 mg once daily and placebo capsules for 4 weeks, or 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 (2).
Shallot extract at 200 μg/mL had an average β-hexosaminidase inhibition rate of 97% while onion extract had 73%. HPLC chromatograms of both plants showed nearly identical patterns of quercetin compounds, such as quercetin 3,4'-diglucoside, quercetin 4'-glucoside, and quercetin (2).
After 4 weeks of treatment, 62.5% of patients in the shallot group and 37.5% of patients in the control group showed improvement in post-treatment VAS. The VAS score was significantly reduced from pre-treatment 5.06± 5.12 to 2.44 ± 5.17 post-treatment in the shallot group (p=0.02) while the VAS scores were 5.38 ± 2.76 and 3.98 ± 2.81 for the pre and post-treatment in the control group (p=0.19). TNSS was significantly reduced in both groups, however, there was no difference between groups (p = 0.18). TOSS was significantly improved only in the shallot group (p = 0.01). Adverse events from shallot were not different from placebo (2).
These results showed that shallot had antiallergic activity and similar quercetin compounds to onion. The shallot oral supplement and cetirizine were shown to improve the overall allergic rhinitis symptoms more than cetirizine alone (2).
Shallots, like other plants in the Liliaceae family, contain several components such as allylsulfides, polyphenols, flavonoids (especially quercetin), and sulfur compounds. Quercetin, a polyphenol and flavonoid might be a key factor in both shallots and onions for their antiallergic properties. Quercetin is found in many foods, including onions, shallots, apples, grapes, berries, broccoli, cherries, citrus fruits, and tea, with the best sources being onions and shallots.
A randomized, placebo-controlled, double-blind study investigated the effects of a 4-week repeated oral intake of a quercetin-containing supplement on allergen-induced reactions and relative subjective symptoms in Japanese adults who complained of eye and nose discomfort (3).
The study included 66 subjects (22-78 years old) with allergic symptoms of pollinosis. The subjects were given the test product (200 mg quercetin) or the control product (placebo) daily for 4 weeks. The Japanese Rhino-conjunctivitis Quality of Life Questionnaire (JRQLQ) scores and other tests were examined in each subject before and after starting the product intake (3).
At 4 weeks after the supplement intake, several scores of JRQLQ, including allergic symptoms, such as eye itching, sneezing, nasal discharge, and sleep disorder, were significantly improved in the quercetin-containing supplement group compared with the placebo group. The JRQLQ score was changed from 25.8 ± 14.6 to 19.1 ± 12.1 in the quercetin-supplemented group compared to from 29.7 ± 13.1 to 26.3 ± 15.0 in the control group (p=0.04). The quality of life of these subjects also significantly improved based on the questionnaire and visual analog scale. Regarding the severity grading of allergic rhinitis: grades of sneezing, rhinorrhea, and disturbance in daily living all showed significant improvement. These results indicated that oral intake of quercetin-containing supplements could effectively reduce some allergy symptoms derived from pollinosis (3).
One study evaluated the effects of a specially formulated quercetin (Quercefit™) plus standard management in subjects with mild-moderate asthmatic attacks and rhinitis. Subjects used either quercetin 1 or 2 tabs/day (250 mg per tablet) in association with standard management or standard management only (control group). After 30 days of management, the presence of the main signs/symptoms of asthma according to the GINA classification system of asthma severity, the need for rescue medication, nasal drops, the use of inhalers, the rhinitis score, and oxidative stress were evaluated (4).
Quercetin + standard management showed superior results compared with standard management alone in controlling, preventing, and reducing daily and night symptoms, maintaining higher peak expiratory flow, and in decreasing peak expiratory flow variability. The supplementary use of quercetin improved additional measures of asthma management, decreasing the use of inhalers, nasal drops, and rescue medications and improving the rhinitis score. Quercetin produced a significantly more evident reduction in oxidative stress compared with standard management. This study showed a potential protective effect of quercetin in decreasing attack frequency and controlling the most common signs/symptoms in the milder cases of asthma (4).
The effect of supplementation with quercetin on cutaneous histamine reaction model ‘Wheal and flare’ and capillary permeability was evaluated in healthy subjects. Supplemented subjects either consumed a full dose (500 mg/day) or a reduced dose (250 mg/day) of quercetin for 3 days, before receiving a cutaneous micro-injection of histamine. After the injection, the wheal and redness areas on the skin were evaluated. Time until the complete disappearance of flares and skin thickness were measured. Microcirculation (as laser Doppler flux) at the injection site was recorded. Capillary filtration in the lower limbs was measured by venous occlusion plethysmography. A comparable group did not take supplementation (control) (5).
Compared with controls, the histamine reaction was reduced in the groups supplemented with quercetin. The higher dose was more effective. The wheal and the redness area were significantly smaller, and the skin thickness had a lower increase in microcirculation (flux) (p<0.05). The wheal area was 1.226 ± 0.22, 1.772 ±0.3, 1.933 ± 0.4 (cm2) for 500 mg, 250 mg quercetin groups, and the control group, respectively. The redness area was 2.05 ± 0.18, 2.24 ± 0.11, and 2.48 ± 0.2 (cm2) for 500 mg, 250 mg quercetin groups, and the control group, respectively. The time for the complete disappearance of flares and skin thickness was 54.5 ± 4.3, 62.2 ± 3.2, and 81.32 ± 6.4 (minutes) for 500 mg, 250 mg quercetin groups, and the control group, respectively. Capillary filtration in supplemented subjects was also significantly lower after 3 days of quercetin consumption, in comparison with controls (5).
This evaluation indicated a dose-related, antihistaminic effect of quercetin and its good safety
profile. The reduced capillary filtration suggested a potential preventive role of quercetin in subclinical and clinical conditions associated with altered histamine release and in edema prevention (5).
These studies showed the potent anti-inflammatory and anti-allergic properties of onion and shallot extracts, attributed to their abundant quercetin content. Research demonstrated the effectiveness of these onion extracts or quercetin in reducing inflammatory responses and alleviating allergic symptoms in patients with allergic rhinitis or asthma. Moreover, when combined with standard treatment medicine, supplementation with onion and shallot extracts consistently led to significant improvements in overall allergic rhinitis symptoms.
References:
1. Dorsch W, Ring J. Suppression of immediate and late anti-IgE-induced skin reactions by topically applied alcohol/onion extract. Allergy. 1984 Jan;39(1):43-9. doi: 10.1111/j.1398-9995.1984.tb01932.x. PMID: 6364880.
2. Arpornchayanon W, Klinprung S, Chansakaow S, Hanprasertpong N, Chaiyasate S, Tokuda M, Tamura H. Antiallergic activities of shallot (Allium ascalonicum L.) and its therapeutic effects in allergic rhinitis. Asian Pac J Allergy Immunol. 2022 Dec;40(4):393-400. doi: 10.12932/AP-300319-0529. PMID: 31421664.
3. Yamada S, Shirai M, Inaba Y, Takara T. Effects of repeated oral intake of a quercetin-containing supplement on allergic reaction: a randomized, placebo-controlled, double-blind parallel-group study. Eur Rev Med Pharmacol Sci. 2022 Jun;26(12):4331-4345. doi: 10.26355/eurrev_202206_29072. PMID: 35776034.
4. Cesarone MR, Belcaro G, Hu S, Dugall M, Hosoi M, Ledda A, Feragalli B, Maione C, Cotellese R. Supplementary prevention and management of asthma with quercetin phytosome: a pilot registry. Minerva Med. 2019 Dec;110(6):524-529. doi: 10.23736/S0026-4806.19.06319-5. Epub 2019 Sep 27. PMID: 31578841.
5. Belcaro G, Cesarone MR, Scipione C, Scipione V, Dugall M, Hu S, et al. Quercetin Phytosome reduces the wheal response to histamine injection. Esperienze Dermatol 2020;22:5-9. DOI: 10.23736/S1128-9155.19.00495-3
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