Palandu (Onion): Ayurvedic Use, Evidence & Safety

TL;DR

Palandu is onion (Allium cepa). WHO's monograph lists age-related vascular support and appetite loss as clinically supported uses, with 50 g fresh onion or 20 g dried drug daily as the dose. Human trials are mostly on quercetin from onion skin: one RCT found a modest 3.6 mmHg systolic drop in hypertensives. Whole-onion evidence is thin.

What it is

Palandu is the Sanskrit name for the onion: the bulb of Allium cepa L. (family Amaryllidaceae, formerly placed in Liliaceae), one of the world's oldest cultivated vegetables and a medicine-food used across Ayurveda, Unani, and folk traditions. The WHO monograph Bulbus Allii Cepae defines the herbal drug as the fresh or dried bulb, with organosulfur compounds (thiosulfinates, cepaenes) and the flavonol quercetin among the constituents of pharmacological interest (WHO Monographs on Selected Medicinal Plants, Vol. 1, 1999). White and red varieties are both used; Ayurvedic texts distinguish rakta palandu (red) and shweta palandu (white) forms.

Traditional use

The WHO monograph organizes onion's uses into three tiers: uses supported by clinical data (principally prevention of age-dependent changes in blood vessels, and loss of appetite). Uses described in pharmacopoeias and traditional systems (treatment of bacterial infections such as dysentery, use as a diuretic, treatment of ulcers, wounds, scars and keloids, asthma, and as an adjuvant in diabetes); and folk uses not supported by experimental or clinical data (WHO Monographs, Vol. 1). In Ayurvedic practice, palandu juice is traditionally instilled in the nostrils for nosebleeds, warmed juice is put in the ear for earache, and heated onion poultices are applied for joint pain and swelling: these are traditional applications, not clinical proof (Seema et al., World J Pharm Res 2017).

What modern research says

Blood pressure (randomized trial of quercetin from onion skin)

In a randomized, double-blind, placebo-controlled crossover trial (n=70 overweight-to-obese adults with pre-hypertension or stage 1 hypertension), 162 mg/day of quercetin from onion skin extract taken for 6 weeks reduced 24-hour ambulatory systolic blood pressure by 3.6 mmHg versus placebo in the hypertensive subgroup, with no significant effect in pre-hypertensives and no changes in cholesterol, glucose, or oxidative markers (Egert et al., Br J Nutr 2015). This tested a quercetin extract, not whole onion: and the effect was modest and limited to people already hypertensive.

Acute vascular effects (randomized crossover trial)

In a randomized, double-blind, placebo-controlled crossover meal study (n=22 overweight-to-obese hypertensive patients), a single 54 mg dose of quercetin from onion skin extract did not change postprandial blood pressure or endothelial function after a high-fat, high-carbohydrate meal (Brüll et al., Eur J Nutr 2016). A single dose does nothing measurable: any effect would require sustained intake.

Immune markers (randomized trial)

An 8-week randomized, double-blind, placebo-controlled trial of onion peel extract found no significant effect on natural killer cell activity or serum cytokines (IL-2, IL-6, IL-12, IL-1β, IFN-γ, TNF-α) in adults (Cho et al. 2024). Onion's popular "immune booster" reputation is not supported by this trial.

Dosage

The WHO monograph gives a daily dosage of 50 g of fresh onion or 20 g of the dried drug, with preparation doses calculated accordingly: a food-scale amount, not a supplement regimen (WHO Monographs, Vol. 1). Quercetin-extract trial doses (54–162 mg/day) apply to extracts, not to onion itself, and do not establish a medicinal dose of palandu.

Safety & contraindications

Allergic reactions such as rhinoconjunctivitis and contact dermatitis have been reported with onion (WHO Monographs, Vol. 1). The WHO monograph reports no general precautions concerning drug interactions, pregnancy, nursing mothers, or pediatric use: which means none were documented, not that safety is proven. As a widely eaten food, onion is generally safe in culinary amounts; concentrated extracts have only short-trial data. People on anticoagulant or antiplatelet drugs should note that onion constituents have shown antiplatelet activity in laboratory and animal studies, so medicinal-strength use deserves a clinician's input.

FAQs

Is palandu just the onion in my kitchen?

Yes: palandu is the Sanskrit name for onion (Allium cepa), and Ayurvedic texts distinguish red (rakta) and white (shweta) varieties (Seema et al., World J Pharm Res 2017). Traditional medicinal uses (juice for nosebleeds, earache, poultices) use the same plant, but in preparations and amounts beyond normal cooking.

Does onion lower blood pressure?

Weakly, at best. One 6-week-per-period crossover RCT found a 3.6 mmHg systolic reduction in already-hypertensive people using 162 mg/day of quercetin extracted from onion skin, not whole onion, while a single-dose study found no effect at all (Egert et al. 2015; Brüll et al. 2016). Eat onions as a healthy food, not as a blood-pressure treatment.

What does WHO actually endorse onion for?

Prevention of age-dependent changes in blood vessels and loss of appetite are the uses WHO lists as supported by clinical data. Dysentery, diuretic use, wounds, asthma, and diabetes-adjuvant use are listed as traditional/pharmacopoeial, and many folk uses (aphrodisiac, earache, fevers) as unsupported by experimental or clinical data (WHO Monographs, Vol. 1).

How much onion did the studies use?

The WHO monograph's dose is 50 g of fresh onion (about half a medium onion) or 20 g dried drug daily: a dietary amount (WHO Monographs, Vol. 1). Trial doses of quercetin (54–162 mg/day) refer to concentrated skin extracts and cannot be translated into onion servings.

Is onion safe in pregnancy?

Onion as food is a normal part of diets worldwide. The WHO monograph documents no specific precautions for pregnancy or nursing: which reflects absence of reported data rather than proven safety of medicinal-strength preparations (WHO Monographs, Vol. 1). Culinary use is uncontroversial; medicinal doses should be discussed with a clinician.

Sources

Disclaimer

This article is for educational purposes only and is not medical advice. Herbal products can interact with medications and are not suitable for everyone. Talk to a qualified healthcare practitioner before use — especially if you are pregnant, breastfeeding, managing a medical condition, or taking prescription medicines.