Acne is the most common skin disorder in the United States, according to the Acne Resource Center. Acne usually develops in the late teens and early 20s, though it can arise in women from 40 to 50 years old. Because of its anti-inflammatory properties, arnica salve may be a suitable treatment for acne.

According to the Acne Organization, the two most common types of acne are non-inflammatory acne, which includes whiteheads and blackheads, and inflammatory acne, consisting of pustules and papules. Skin Care Physicians explains that acne is caused when the skin produces too much oil. The oil blocks the pores, causing bacteria to flourish and leading to inflammation and the buildup of pus.

Arnica is a perennial plant with bright yellow flowers. According to the University of Maryland Medical Center, it has been used for medicinal purposes for around 500 years. It is used topically to treat a wide range of conditions including sprains, bruises, muscle aches, insect bites, acne and to heal wounds. It is also used in homeopathic preparations, which are diluted to the extent that there is no detectable amount of the plant in the preparation.

According to the NDRI, arnica may be used to treat acne possible due to its antiseptic properties as it can control the build-up of bacteria. The University of Maryland Medical Center recommends ointments and salves which contain 20 to 25 percent or a maximum of 15 percent arnica oil which should be derived from on part dried flower and five parts vegetable oil.

According to ndri.com, the use of arnica may cause inflammation of the skin. You should not take arnica orally as it could cause stomach irritation, dizziness, cramping, tremors, dangerous increase in blood pressure and irregular heart beat. Arnica is contraindicated for those taking the blood thinner warfarin -- Coumadin -- . Before using arnica to treat your acne, you should consult your family practitioner.

Ndri.com cites a study published in Facial Plastic Surgery by Drs. Pribitkin and Boger in 2001 that shows that although arnica has an anti-inflammatory effect, it should not be used on broken skin. This suggests that arnica is not suitable as a treatment for all forms of acne. More research is needed.