Some of the impressive benefits of arnica oil include soothing inflammation, boosting hair growth, stimulating the immune system, eliminating pain, protecting the heart, relieving headaches, increasing circulation, easing nervous disorders and preventing chronic disease. There are a few side effects associated with the use of arnica oil, namely skin irritation, bleeding, gastrointestinal distress, nervous and cardiovascular side effects, pregnancy complications, and dizziness. Many of the more severe side effects are experienced when this oil is consumed or inhaled, which is never recommended for this potent oil.
What is Arnica Oil?
Arnica oil is produced from the blossoms of a perennial flowering plant called arnica, which belongs to the daisy family. The plant is native to Europe, but it is also found widely in the United States. The most commonly used species of arnica for the production of arnica oil is Arnica montana, which produces a pale yellow oil that is extremely useful. It is often included in cosmetic and dermatology products, as well as soaps and shampoos, but only in minimal, diluted forms. Using pure arnica oil is only appropriate for topical use, and even then, allergic reactions may occur. The many benefits (and potential side effects) of this oil are due to the high levels of monounsaturated and polyunsaturated fats, such as myristic, palmitic, linoleic and oleic acids, as well as thymohydroquinone, thymol and other volatile compounds. 
Benefits and Uses of Arnica Oil
Arnica oil is often used by people who are seeking relief from arthritic pain, chronic inflammation, hair loss, bruises, a weak immune system, high blood pressure, high cholesterol, headaches, poor circulation, nervous conditions, oxidative stress, and acne, as well as those recovering from illness or surgery.
The topical application of arnica oil is common for inflammatory conditions, such as eczema, psoriasis, rosacea and even acne. The monounsaturated fats found in this oil, along with thymohydroquinone, are able to soothe inflammation on the skin when used in moderate amounts. The antioxidant elements of this oil can also help lower oxidative stress and prevent signs of aging, such as wrinkles and blemishes. 
The analgesic properties of this oil are well known, and when a few drops applied on the temples or the base of the neck, it can quickly soothe migraines and headaches. Although it may be tempting to use this oil in an aromatherapy treatment for headaches or stress, do not inhale diffused arnica oil. 
Boosts Cardiovascular Health
Monounsaturated and polyunsaturated fats are known as “good” fats, which can help lower blood pressure and cholesterol levels. Oleic acid and linoleic acid are particularly good for reducing inflammation and promoting a healthier metabolism, which can further reduce your risk of atherosclerosis and other heart ailments. 
Reduces Arthritis Pain
One of the unique abilities of arnica oil is its ability to stimulate white blood cell production. These defensive cells can also help reduce inflammation in joints and muscles, which can commonly accompany arthritis. 
Heals Bruises & Injuries
When you topically apply this oil to injuries like bruises and strained muscles, it can quickly stimulate circulation to those areas, including the resources and oxygen needed to produce healthy new cells and heal broken blood vessels. 
The stimulating nature of arnica oil can boost your circulation by reducing coagulation in your cardiovascular system, helping to lower blood pressure and prevent blood clots from forming. This can also increase energy and promote healing throughout the body. 
Prevents Hair Loss
Arnica oil is rich in key nutrients, vitamins and fatty acids that can boost hair growth, while also protecting the scalp against infections and oxidative stress, which can often lead to premature hair loss. Arnica hydrogel stimulates the hair. Moreover, Arnica Montana is also used for herbal and homeopathic medicine for hair growth stimulation in the form of arnica oil and arnica shampoo. It helps to rejuvenate the scalp, foster hair follicles by improving blood flow and prevent premature hair fall.  
Boosts Immune System
Numerous studies have found that arnica oil is able to stimulate the production and activity of white blood cells, which are the first line of defense for the body’s immune system. This can increase bacterial and viral resistance, both in topical applications and in the rest of your organ systems, as this oil takes less than 3 hours to be completely absorbed by the skin and dispersed throughout the body. 
Has Antioxidant Properties
Although much of the attention on arnica oil is paid to the monounsaturated and polyunsaturated fatty acids it contains, this oil also boasts sesquiterpenes, thymol and other potent antioxidants that can protect you against chronic diseases. 
Arnica Oil Side Effects
Use of arnica oil does come along with certain side effects, such as certain bleeding disorders, skin inflammation, gastrointestinal distress, cardiovascular and nervous system complications, dizziness, and problems with pregnancy.
Internal consumption of pure arnica oil is not recommended and can be toxic when ingested in high doses. If you do choose to use a diluted form of arnica oil, it can cause gastrointestinal distress, cramping, bloating, diarrhea, nausea, and vomiting.
In excessive amounts, pure arnica oil can cause internal hemorrhaging, which can be fatal. As mentioned, internal consumption of this oil is not recommended under any circumstances, unless specifically approved by a doctor.
Arnica oil is not recommended for women who are pregnant or breastfeeding, due to the potency and stimulating elements of the oil, as it can pass toxins to the fetus/infant or induce premature labor.
The stimulating nature of this powerful oil can cause irregularities in a heartbeat and result in unusual palpitations in some people, especially those who already have heart issues. Don’t use this oil before speaking with your doctor about your specific health condition.
There have been limited reports of complications with the nervous system when using arnica oil, particularly if you already suffer from a nervous disorder, such epilepsy or muscle spasms.
Many people think to use natural oils to protect the wounds from infection and speed up the healing process. However, using arnica oil on open wounds can be toxic and should be avoided. Even normal use on the skin is known to cause inflammation, due to the potency of this oil’s constituents.