People should avoid sorrel if they have known allergies to sorrel (Rumex acetosa) or any member of the Polygonaceae family. Sorrel's pollen is a potential respiratory allergen and may trigger allergic reactions or bronchial asthma. Signs of allergy include rash, itching, and shortness of breath.
Side Effects and Warnings
There is limited evidence for the safety of sorrel consumed alone. Sorrel seems to be well tolerated by most people. Some people may experience stomach pain or cramping, vomiting, nausea, and diarrhea. Other side effects may include difficulty breathing or skin irritation caused by sorrel allergies. Rarely, kidney stones or kidney damage may occur, causing either frequent urination or lack of urination. Low levels of calcium in the blood may also occur, which can lead to muscle spasms. Dizziness, gastrointestinal tract damage, and liver disease are also possible side effects. Many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery. Large doses of sorrel should be avoided; they have been associated with reports of toxicity and death, possibly caused by oxalates found in sorrel.
The combination formula Sinupret®, which contains sorrel in combination with gentian root, European elderflower, verbena, and cowslip flower, is reported to be well tolerated but has been associated with infrequent few cases of gastrointestinal upset. Essiac®, an herbal combination product that contains sorrel, has also caused minor side effects.
Caution should be used among patients with kidney conditions or stomach.
Sorrel is possibly unsafe in children due to its oxalic acid content; ingestion of rhubarb leaves, another source of oxalic acid, is reported to have caused death in a four-year-old child.
Pregnancy and Breastfeeding
There is not enough scientific evidence to recommend using sorrel during pregnancy or breast-feeding. Many tinctures contain high levels of alcohol and should be avoided during pregnancy. Sinupret® did not increase the risk of birth defects in one study.
Adults (18 years and older):
There is a lack of established dosages for sorrel taken alone. In small doses, sorrel is likely safe. However, due to reports of significant oxalate toxicity when taken in larger doses, caution is advised.
Sorrel is most often used medicinally as a part of combination formulas. For cancer, a dose of 30 milliliters (two tablespoons) of Essiac® tea has been taken 1-3 times daily. For sinus infections, 1-2 tablets of the combination product Sinupret® taken by mouth 1-3 times daily for two weeks has been studied. Sinupret® is a combination product containing sorrel, gentian root, European elderflower, verbena, and cowslip flower. Fifty drops of an alcohol-based (19%) Sinupret® tincture has also been taken by mouth three times daily.
Children (younger than 18 years):
There are not enough scientific data to recommend sorrel for use in children, and sorrel is not recommended because of potential side effects and toxicity.
Interactions with Drugs
In general, prescription drugs should be taken one hour before or two hours after sorrel to reduce the likelihood of drug interactions. Many tinctures contain high levels of alcohol and may cause nausea or vomiting when taken with metronidazole (Flagyl®) or disulfiram (Antabuse®).
In theory, herbs with high tannin content, such as sorrel, should not be used in combination with alkaloid agents, such as atropine, galantamine, scopolamine (Transderm-Scop®), or vinblastine.
Use of the antibiotic doxycycline with Quanterra® Sinus Defense or Sinupret® may have a positive interaction and improve outcomes in patients with acute bacterial sinusitis.
Sorrel is popularly taken in Essiac® as a cancer therapy. In theory, sorrel and sorrel combination products (e.g. Essiac®, Flor-Essence®) may interact with other cancer therapies.
Excessive urination has been reported with the use of sorrel, and may add to the effects of diuretics, such as hydrochlorothiazide or furosemide (Lasix®).
In large amounts, ingestion of sorrel may lead to kidney stones, kidney damage, or liver damage and should be avoided with agents that are toxic to the kidney or liver.
Sorrel may also interact with antivirals or gastrointestinal drugs.
Interactions with Herbs and Dietary Supplements
In theory, sorrel should be administered separate from other herbs or supplements, especially alkaloid agents, such as belladonna. Sorrel may impair absorption of calcium, iron, and zinc supplements.
Excessive urination has been reported with the use of sorrel. Sorrel may add to the effects of diuretic herbs such as artichoke, celery, or dandelion.
In large amounts, ingestion of sorrel may lead to kidney stones, kidney damage or to liver damage, and should be avoided with agents that are toxic to the kidney or liver.
Rhubarb and shamrock are sources of oxalate, and may add to the toxic effects of oxalate in sorrel.
Sorrel may also interact with antibacterial, anti-cancer, antiviral, and gastrointestinal herbs and supplements.