Side Effects of Arnica Tablets

Although people more commonly use arnica as a tincture, a salve for external use, you may use arnica as a low-dose tablet to help combat pain. The University of Maryland Medical Center states that taking arnica internally in high doses may induce severe side effects. The organization recommends taking it this way only with the direct supervision of a doctor. Arnica may help treat infections and help with pain associated with inflammation. You may experience arnica side effects.

Nauseaus woman holding her stomach and mouth (Image: deeepblue/iStock/Getty Images)

Stomach Irritation

Usually arnica is not taken by mouth because of its highly irritating effect on your digestive system and its lining, called the mucosa, indicates. Taken in a low-dose homeopathic form, arnica still may produce irritation in your stomach that may cause mild pain. Your appetite may decrease because of this. This stomach irritation should go away on its own within a day or two if you have used a low-dose form of the supplement.


You may experience loose stools when you use arnica tablets. Diarrhea frequently occurs when your body needs to adjust to a new substance within it. This common side effect typically lasts a couple of days when first taking arnica by mouth. If diarrhea manifests as a severe or continual side effect of arnica, speak with your physician.


Again, arnica taken internally tends to produce stomach irritation. This may cause nausea and a need to vomit. Your body may feel the need to vomit up the arnica. This common side effect may occur when first ingesting the arnica at a lower dose, reports.


Nosebleeds could occur as a non-serious side effect of arnica, the American Cancer Society notes. Report any sign of a nosebleed to your doctor because it could indicate an internal bleed exists. You should stop ingesting arnica until you see your doctor.


Dizziness could occur as a side effect of arnica if you take it orally. You also need to report the sensation of motion or imbalance to your doctor because it could represent a serious problem related to an underlying health issue.

Heart Irregularities

Arnica may cause an arrhythmia or heart rhythm irregularity, the American Cancer Society indicates. Your heart may beat irregularly, it may slow down or speed up, or you may feel palpitations. Talk with your physician if you experience a noticeable difference in how you feel associated with the beating of your heart. Heart irregularities can cause death and need immediate evaluation.


Tremors may occur as a side effect of arnica taken by mouth, the American Cancer Society reports. You may feel your arms and legs have small uncontrolled movements. If this occurs call your doctor right away to be evaluated medically. Tremors are a sign your central nervous system has been affected in some way.

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