My friend brought me a combination of belladonna and arnica. What are the uses?

Homeopathic remedies. I'm guessing you may have received this as a lotion or cream. It's a combination remedy which can be topically applied to sprains and bruises -- it may decrease pain, inflammation and bruising. Do not apply it to broken skin or open wounds. Arnica and belladonna are each homeopathic remedies which can be used in acute illnesses and in long-term chronic cases. A homeopath can help you with this.
Belladonna+ arnica. Belladonna "b"and arnica each has topical pain relieving effects on the skin, for conditions deeper down like muscle spasm, pain or other tissue pains. Not dangerous but u are not to swallow it, ever! topical b. May quiet inflamed nerves, thus reducing pain. If the pains are too major, this usually homeopathic strength gel may not bring all the relief you need+may need to take other pain meds.