Blessed thistle (generic name)
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SafetyDISCLAIMER: Many complementary techniques are practiced by healthcare professionals with formal training, in accordance with the standards of national organizations. However, this is not universally the case, and adverse effects are possible. Due to limited research, in some cases only limited safety information is available.
Allergic reactions to blessed thistle including rash may occur, as well as cross-sensitivity to mugwort and echinacea. Cross-reactivity may also occur with bitter weed, blanket flower, chrysanthemum, coltsfoot, daisy, dandelion, dwarf sunflower, goldenrod, marigold, prairie sage, ragweed, and other plants in the Asteraceae/Compositae family.
Side Effects and Warnings
Blessed thistle is generally considered to be safe when used by mouth in recommended doses for short periods of time, with few reported side effects. Direct contact with blessed thistle can cause skin and eye irritation.
Blessed thistle taken in high doses may cause stomach irritation and vomiting. Blessed thistle is traditionally believed to increase stomach acid secretion and may be inadvisable in patients with stomach ulcers, reflux disease (heartburn), hiatal hernia, or Barrett's esophagus.
Blessed thistle contains tannins. Long-term ingestion of plants containing tannins may cause gastrointestinal upset, liver disease, kidney toxicity, or increased risk of developing esophageal or nasal cancer. The effects in humans of blessed thistle tannins are not known.
Laboratory studies suggest that blessed thistle may increase the risk of bleeding, although effects in humans are not known. Caution is advised in patients with bleeding disorders or taking agents that may increase the risk of bleeding. Dosing adjustments may be necessary.
Many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery.
Pregnancy and Breastfeeding
Blessed thistle has been used traditionally to stimulate menstruation and abortion, and therefore should be avoided during pregnancy. Although blessed thistle has been used historically to stimulate breast milk flow, it is not recommended during breastfeeding due to limited safety information. Reliable research is lacking in these areas.
Many tinctures contain high levels of alcohol and should be avoided during pregnancy.
Interactions with Drugs
Traditionally, blessed thistle is believed to stimulate stomach acid secretion and it may reduce the effectiveness of drugs such as cimetidine (Tagamet®), famotidine (Pepcid®), nizatidine (Axid®), or ranitidine (Zantac®).
Based on laboratory studies, blessed thistle may increase the risk of bleeding when taken with drugs that also increase the risk of bleeding (although effects in humans are not known). Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin®) or heparin, anti-platelet drugs such as clopidogrel (Plavix®), and non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).
Interactions with Herbs and Dietary Supplements
Based on laboratory studies, blessed thistle may increase the risk of bleeding when taken with herbs or supplements that are believed to increase the risk of bleeding (although effects in humans are not known). Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this may not be proven in most cases.