There is insufficient evidence to prove that bruises treated with arnica gel heal faster than untreated bruises, according to WebMD. Some studies show that arnica gel may be used to effectively treat pain and swelling of arthritis in the hands and knees.
When applied topically, arnica gel can cause skin irritation and trigger allergic reactions. Although sometimes used as a food flavoring, pure arnica is toxic and is classified by the U.S. Food and Drug Administration as an unsafe herb.
The Mayo Clinic recommends ice packs and elevation to treat bruises. Acetaminophen or ibuprofen may be used to manage pain and swelling. Unless the skin is broken, no bandage is required.