Arnica is a perennial plant in the Asteraceae family; it is native to Europe and North America. There are multiple species of arnica, but the most commonly used in commercially sold products is Arnica montana, which typically grows at high altitudes (up to 3,000 m altitude).[1][2]
Arnica is mainly applied topically as a gel or a cream, but it can also be found in oral homeopathic preparations, albeit in extremely diluted forms.[1][1]