Benefits
Traditional herb for leg heaviness and discomfort
The EU registers melilot tea and powder only as a traditional herbal medicine to relieve discomfort and heaviness of the legs from minor vein circulation problems. The EU assessors judged the open studies, which lacked proper control groups and objective measures, too weak to show efficacy, so this rests on long use.
Leg heaviness and ankle swelling in an open 15-day comparison
In a 15-day open study of people with leg vein problems, the 20 who took 200 mg a day of melilot extract had less ankle swelling, fewer night cramps and less leg heaviness, as described by the EU assessors. The assessors called its clinical relevance doubtful, and a Cochrane review comparing this group with ozonated bath therapy found little or no difference in pain or swelling, at very low certainty.
Bruising and nose-area swelling after facial cosmetic surgery
In a small controlled study of 46 people having nose and eyelid surgery together, those given oral melilotus extract had less bruising at day 7 and less swelling beside the nose at days 4 and 7 than untreated patients, while eyelid swelling did not differ. An eye surgery society review concluded the evidence does not support melilotus for bruising after such surgery.
Arm circumference in an open study after breast surgery
In an open study of women with long-term arm swelling after lymph node removal for breast cancer, 400 mg a day of a coumarin-rich melilot extract for 6 months reduced upper arm circumference by a median of about 5% in those treated per protocol. Only 4 untreated women served as a comparison and several dropped out.
Swelling measures in blends with bromelain, rutin or diosmin
Blends containing melilot have been tested after facial fracture surgery, after prostate surgery and in long-term limb swelling. Results ranged from less facial swelling to no difference in leg volume, and one study had no control group. Because each product held several actives, none shows what sweet clover itself adds.
Inflammation markers in rabbits and cultured cells (animal and lab studies)
In rabbits, an injected melilot extract with 0.25% coumarin lowered markers of acute inflammation about as much as coumarin; some effects matched hydrocortisone and others were weaker. Compounds isolated from the herb lowered inflammatory signals in mouse immune cells in a dish. These injected and cell results have not been tested by mouth in people.
Mechanism of action
Coumarin released as the herb dries
In the fresh plant, coumarin is stored mainly as sugar-bound o-hydroxycinnamic acid glucosides such as melilotoside. During drying, a glucosidase enzyme frees the acid, which closes into coumarin. This is why dried melilot smells of hay and why its coumarin content, 0.3 to 0.9% in the EU assessment, depends on drying.
Proposed effects on swelling, still unclear
The EU assessment states that the constituents behind melilot's effects are not known. Coumarin was long credited with its anti-swelling action, and coumarin has drawn macrophages into swollen, injured or inflamed tissue, though how is not clarified. All the animal data the EU assessors reviewed used injected extracts, not oral use.
Coumarin is cleared by the liver enzyme CYP2A6
In humans, CYP2A6 turns most coumarin into 7-hydroxycoumarin, which is excreted in urine. A minor ring-opening route forms a reactive epoxide that is thought to drive liver toxicity. CYP2A6 activity varies with genes and other factors, and whether poor metabolizers face more liver risk remains unproven.
Coumarin versus dicoumarol
Coumarin and its simple relatives in sweet clover do not affect blood clotting, according to the EU assessment. Dicoumarol, a blood thinner, forms only when the plant is spoiled by fungi; moldy sweet clover silage containing it has caused fatal bleeding in cattle.
Clinical trials
Three-arm controlled study at a Chinese university hospital: one surgeon performed augmentation rhinoplasty and double-eyelid surgery in one operation, then patients received oral melilotus extract, dexamethasone or neither, and two investigators scored bruising and swelling independently on days 1, 4 and 7. The abstract does not state how patients were assigned, the extract dose, patient blinding or funding. (Xu et al. 2008, Aesthetic Plast Surg)
46 adults having simultaneous rhinoplasty and blepharoplasty: 16 melilotus extract, 16 dexamethasone, 14 untreated controls.
Compared with controls, the melilotus group had lower upper eyelid, lower eyelid and nose-area bruising scores at day 7 and less nose-area swelling at days 4 and 7, but eyelid swelling did not differ. Dexamethasone lowered swelling on days 1 and 4 but not bruising. A 2022 American Academy of Ophthalmology review found the benefit at day 7 only, not days 1 and 4, and concluded the evidence does not support melilotus for bruising after eye and face surgery.
Open clinical study in Italy, published in Italian with an English abstract: 400 mg a day of a coumarinic extract of Melilotus officinalis containing 8 mg coumarin, taken once daily for 6 months, with upper arm circumference measured at 3 and 6 months. No randomization or placebo. (Pastura et al. 1999, Clin Ter)
24 women with chronic upper arm lymphedema after axillary lymph node removal for breast cancer; 21 eligible, 14 treated per protocol, 4 untreated women followed as controls.
Of the 14 treated per protocol, 11 had a reduction in arm circumference and 3 had no change; the median reduction was about 5% (p = 0.048), and symptoms improved in 12. The 4 untreated women worsened. Three women had brief digestive side effects and three were lost to follow-up.
Open-label study in Italy of a blend (Brovas), described as randomized without details of the method: bromelain 700 mg a day, Aesculus hippocastanum 370 mg a day and Melilotus officinalis 200 mg a day standardized to 20% coumarin, one tablet twice daily for 15 days, versus no product. The authors note it could not be run double-blind; they state that the sponsor, which is not named, had no involvement that could have influenced the outcome; the product is made by AGAVE group, Bologna. (Consorti et al. 2024, J Clin Med)
100 patients aged 15 to 80 having surgery for facial fractures, 50 per group.
The blend group had less facial edema in the first and second weeks after surgery, faster complete resolution of swelling, a smaller loss of mouth opening and fewer days of anti-inflammatory painkillers (median 2 versus 4 days). With three actives and no placebo, the result cannot be credited to sweet clover.
Exploratory randomized open-label trial in Italy, not registered: one tablet a day of a blend (Meliven Top) for one month after robot-assisted prostatectomy with extended pelvic lymph node removal, versus standard care alone; leg volume was measured by assessors blinded to group. No external funding. (Montanaro et al. 2026, J Robot Surg)
100 men having robot-assisted radical prostatectomy for prostate cancer; 98 completed follow-up.
The primary outcome, lower-limb volume change at 1 and 3 months, did not differ between groups. Genital pain at 1 month (2% versus 18%, p = 0.008) and persistent genital swelling at 3 months (0% versus 8%, p = 0.041) were less common with the blend, but these were secondary outcomes recorded as present or absent by clinicians who knew each patient's group. Lymphocele rates were similar and no adverse events occurred.
Uncontrolled study in Rome of a blend with 100 mg Melilotus, 300 mg rutin and 100 mg bromelain for six months, with liver blood tests; the abstract gives the coumarin content as 20 grams, an apparent misprint. The authors report no relevant financial relationships. (Michelini et al. 2019, Lymphology)
52 patients with stage I or II primary or secondary lymphedema (31 legs, 21 arms).
At six months, pitting disappeared in 72% of cases, limb circumference fell by an average of 4.2 cm and tissue thickness on ultrasound by 29%, while Stemmer's sign was unchanged. Liver tests did not change and no side effects were seen. Without a control group, these changes cannot be credited to the blend.
Animal study in Romania of a Melilotus officinalis extract containing 0.25% coumarin, compared with hydrocortisone and with coumarin, given before turpentine-induced inflammation; the EU assessment notes the extract was injected into the abdomen. (Pleşca-Manea et al. 2002, Phytother Res)
Male rabbits; no human participants.
The extract reduced activation of circulating phagocytes and lowered citrulline production, effects similar to hydrocortisone and coumarin; its damping of the bone marrow acute phase response was weaker than hydrocortisone and similar to coumarin. Injected doses in rabbits do not show an effect of oral use in people.
Laboratory study in China isolating nine compounds, including two new p-hydroxybenzoic acid glycosides, from a 70% ethanol extract of the aerial parts, then testing antioxidant activity, inflammatory signals in mouse macrophages and growth of a breast cancer cell line. The authors state the study was partly supported by funding sponsors. (Liu et al. 2018, Molecules)
No human participants; chemical assays, mouse RAW 264.7 macrophages and MCF-7 cells.
All nine compounds reduced LPS-induced nitric oxide and prostaglandin E2 production by suppressing iNOS and COX-2, and had varying effects on TNF-alpha and IL-6. Five compounds showed stronger antioxidant activity than the rest, and two had the strongest effect on the cancer cells. These are test-tube results with isolated compounds.