When you sprain, twist, or strain something - and the injury isn't serious enough for medical attention - what do you do to relieve the pain?

If you're like most people, you run to the medicine cabinet and choke down a handful of ibuprofen (panadol) or acetaminophen (paracetamol). But these products have potential side effects (some very serious - like liver damage and death). So next time, try a natural approach. Rub arnica gel (available at most natural foods stores) on the injured area. In a relatively short time, the pain, bruising, and swelling will be diminished. Source: Early to Rise

Arnica' usually refers to Arnica montana , a mountain plant used for relief of bruises, stiffness, and muscle soreness in herbal medicine. Arnica is widely used as a salve for bruises and sprains, and sometimes as a tincture, for the same anti-inflammatory, pain-relieving purposes. It is available in natural/health food stores, most commonly in gel form, to be applied to the affected area approximately three times daily.
Reproduced from Wikipedia http://en.wikipedia.org/wiki/Arnica

The active components in arnica are sesquiterpene lactones, which are known to reduce inflammation and decrease pain. Other active principals are thymol (an essential oil), flavonoids, inulin, carotenoids and tannins.

Arnica works by stimulating the activity of white blood cells that perform much of the digestion of congested blood, and by dispersing trapped, disorganized fluids from bumped and bruised tissue, joints and muscles.

Arnica is known to stimulate blood circulation and can raise blood pressure, especially in the coronary arteries. The plant is used externally for arthritis, burns, ulcers, eczema and acne. It has anti-bacterial and anti-inflammatory qualities that can reduce pain and swelling, improving wound healing.
Reproduced from: http://www.primary.net/~gic/herb/arnica.htm