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Horsetail: contraindications and side effects
October 16, 2023
Also known as 'field horsetail', Equisetum arvense is widely used in herbalism due to its various health benefits known since ancient times. It is currently available in the form of capsules, tablets and tea.
What are the contraindications for horsetail?
Taking horsetail-based dietary supplements is not recommended for people with proven hypersensitivity to one or more components of the product. In addition, pregnant and breastfeeding women should avoid taking it.
Regarding the possible toxicity of horsetail, there are no specific studies to refer to yet. However, since the plant contains nicotine, its use should be avoided by people who are allergic to this substance.
The use of remedies containing horsetail should also be avoided by people with edema due to heart or kidney disease. When using compresses, especially in the case of large skin injuries or those of unknown origin, it is advisable to obtain the opinion of the treating doctor beforehand.
What are possible side effects?
One of the few side effects associated with horsetail concerns the possible activation of thiaminases (I and II). These are a few of the enzymes that antagonize thiamine, better known as vitamin B1. Therefore, long-term or excessive use of 'Field Horsetail' products or supplements, particularly in the form of oral intake, could lead to vitamin B1 deficiency in individuals with low thiamine levels. For this reason, people who suffer from alcoholism should also not take horsetail products in any form to avoid possible vitamin B1 deficiency.
In people with diabetes, however, 'field horsetail' can cause a drop in blood sugar levels (hypoglycemia).
Finally, horsetail can sometimes cause an excessive drop in potassium levels in people who already suffer from hypokalemia and interfere with the body's natural excretion of lithium. There is no information regarding side effects or contraindications regarding horsetail and the thyroid.