If you consider funding New Age quack cures to be immoral (which I do), then yes, using Anica Montana is immoral.

For those of you who have never heard of it, arnica montana (also known as leopard's or wolf's bane) is an herb used on minor injuries, to reduce swelling,  prevent muscular soreness and alleviate postoperative pain. As an herbal medicine, it has been in use for about 200 years. According to double-blind studies, the most reliable tests known to science, the herbal version has demonstrated that it relieves pain in osteoarthritis patients.

However, the homeopathic version which your friend is using is a whole different story.

This report appearing in the UK's Daily Mail documents a study conducted at Exeter University by England's only professor of complementary medicine, Dr. Edzard Ernst. Published in the Journal of the Royal Society of Medicine, Ernst found that homeopathic arnica, which contains arnica in an extremely diluted form, was essentially useless.

"It will help people to look for more effective treatments and save money by not buying homeopathic arnica," he stated bluntly.

His study followed three groups of 64 patients who were having surgery on their wrists due to carpal tunnel syndrome. One group received a high dose of arnica, the second a low dose, and the third was given a placebo. The results showed no significant differences in pain, swelling or bruising between the groups.

Arnica Montana plant

Your friend may want to switch to the herbal version, which is generally safe (if you're not allergic to it) when used as a cream or lotion on the skin.  Just be careful not to use it too much because long-term use has been found to cause a variety of skin problems such as eczema, peeling, and blisters.

It is rarely taken internally because it can cause dizziness, tremors, heart regularities, and vomiting. Large doses can be fatal.

(The homeopathic version is in pill form but these are the equivalent of sugar pills with an "Arnica Montana" label on them so they're essentially harmless.)

The way I see it, as long as we keep buying these homeopathic drugs, we keep these people in business. Even though I'm sure they mean well, science simply does not support the efficacy of homeopathic preparations and we owe it to ourselves as well as to the practitioners to quit buying them.