Arnica oil is a popular holistic treatment for dandruff. Dandruff (seborrheic dermatitis) is caused by scalp irritation, dry skin, or a fungal infection. Applying arnica oil may improve your scalp's texture and relieve symptoms of itching and inflammation, according to anecdotal evidence. Arnica is used topically for a wide range of conditions, including bruises, sprains, muscle aches, wound healing, superficial phlebitis, joint pain, inflammation from insect bites, and swelling from broken bones. More recent studies suggest it may also be helpful in the treatment of burns.