Which plant's flowers are used in a topical gel to reduce bruising and swelling? Arnica is the answer.
The name usually refers to Arnica montana, a yellow-flowered European plant in the sunflower family, Asteraceae. Traditional herbal preparations use extracts of its flower heads, especially in creams, ointments, and gels intended for bruises, sprains, and localized swelling.
Arnica has a complicated evidence and safety record. Some topical studies have investigated concentrated preparations for pain and swelling, but results vary by product and strength. Homeopathic arnica is different: it is diluted so extensively that it generally contains no measurable plant material, and clinical reviews have found it no better than placebo for many uses.
A common mistake is assuming arnica is safe to swallow or apply to broken skin. The plant contains helenalin and can cause poisoning or dermatitis; traditional topical products are meant for intact skin and should be used according to their label. Arnica is also unrelated to the poisonous plant genus Aconitum, despite overlapping common names such as “wolf’s bane.”