The whole plant, but especially the flowers and the root, is antiecchymotic, antiphlogistic, irritant, nervine, sternutatory, tonic and vulnerary[61, 172].
This plant is used in North America in much the same way as A. montana is used in Europe. These uses are as follows:-
Arnica has a long history of herbal use, especially as an external treatment for bruises and sprains[232, 238] – it is an ingredient of a number of proprietary preparations[238. Internally, it has been used in the treatment of heart complaints and as a booster for the immune system. Arnica increases local blood supply and accelerates healing, it is anti-inflammatory and increases the rate of absorption of internal bleeding. Generally the plant is nowadays only recommended for internal use as a homeopathic medicine, principally for treating shock, injury and pain. If used as a decoction or tincture it stimulates the circulation and is valuable in the treatment of angina and a weak or failing heart, but it can be toxic even at quite low doses and so is rarely used this way.
The flowers are the part most commonly used[4, 232], they are harvested when fully open and dried – the receptacles are sometimes removed since these are liable to be attacked by insects. The root is also used, it is harvested after the leaves have died down in the autumn and dried for later use.
The whole plant is antiecchymotic, antiphlogistic, nervine, sternutatory, vulnerary[4, 7, 9, 46, 165]. Although a very valuable remedy, it should be used with caution. It has been known to cause contact dermatitis when used externally and collapse when taken internally. Only take it internally under the supervision of a qualified practitioner.
The freshly crushed flowers cause sneezing if inhaled.
The leaves have also been smoked as a tobacco, though it is unclear whether this was for medicinal reasons
The whole plant, harvested when in flower, is used in homeopathic remedies. It is especially useful in the treatment of traumatic injuries, sores and bruises.