The health benefits of Parsley Essential Oil can be attributed to its properties as a potentially antimicrobial, anti-rheumatic, anti-arthritic, antiseptic, astringent, carminative, circulatory, detoxifier, digestive, diuretic, depurative, emmenagogue, febrifuge, hypotensive, laxative, stimulant, stomachic and uterine substance.
Has anyone read the world-famous comic book Adventures of Asterix and Obelix by Uderzo and Gossinni? If not, here is a quick summary. It presents a scenario of Rome and some Gallic villages during the reign of Julius Caesar. In that book, every now and then, you will find Obelix gobbling down those roasted wholesome wild boars garnished and decorated with parsley leaves (its a different part of the story than when he uses those parsley branches for cleaning his ears).
I’m not kidding when I saw that this comic book proves that parsley was in use since those ancient times! Okay, you caught me. The comic may not be 100% historical fact, but it is true that parsley is one of the oldest spices known to man. It has been and still is, in use both as seeds and fresh leaves, particularly for garnishing meat, and other foods as well. It is also used for decorating them. It has a refreshing and appetizing herbaceous flavor that comes from its essential oils. This essential oil is derived from its dried seeds by steam distillation and contains apiole, myristicin, pinene, and tetramethoxyally benzene as its chief components. By the way, the botanical name of Parsley is Petroselinum sativum. 
This herb, apart from being so widely used as a spice and condiment, has a lot of medicinal properties to offer, which are also mainly due to the properties of its essential oil.
Health Benefits of Parsley Essential Oil
May Prevent Microbial Infections
Where there are microbes, there are infections and diseases, but where there is parsley essential oil, there are no microbes. But why? Perhaps because this oil has extensive antimicrobial properties. That is, this oil has certain components which can kill microbes and inhibit their growth. Therefore, it can effectively give protection against a multitude of infections. 
May Relieve Arthritis Pain
Rheumatism and arthritis are two diseases that are caused by two main reasons, namely, the accumulation of uric acid in the muscles and joints, as well as obstructed blood circulation. The essential oil of parsley has certain properties which can help you with both of these causes. First of all, it is a detoxifying agent and a depurative, which is due to the diuretic and stimulant properties that it possesses. While a detoxifier speeds up the removal of toxins from the body, a depurative purifies and refreshes the blood. Now, as a diuretic, it may also increase urination, and as we all know, the toxic and unwanted substances of the body such as excess water, salts, and uric acid are removed through the urine. Then, as a stimulant, it stimulates the flow of blood or increases circulation. This helps in two ways. First, it warms up the body, and second, it does not let uric acid accumulate at any particular place, giving relief from the pain of arthritis and gout.
May Prevent Sepsis
Wounds and certain soft and sensitive internal organs can become septic due to infection by microbes. The danger is greater when the wound is dirty or caused by rusty iron objects. Sepsis brings pain accompanied by cramps, convulsions, and even hydrophobia (if it develops into tetanus). Its cure lies in eliminating microbes and inhibiting their growth in the affected area and this is exactly what parsley oil does. It stops microbes from multiplying and eliminates them.
Research published in Genetics and Molecular Research found that parsley essential oil has powerful antibacterial and antifungal properties. It was found effective against seven strains of bacteria and eight strains of fungi. 
May Act as an Astringent
Astringency is a property by virtue of which a substance can induce contractions in the tissues and muscles. The effect of an astringent can be local or on the whole body. Some astringents, such as the synthetic ones like fluorides which are added in toothpaste, may induce local contraction of the gums. Others, most of which are natural or herbal, such as those found in guava leaves and many essential oils, can be ingested and induce contractions in internal organs and the whole body, as the astringent is carried to all the tissues by the blood. The essential oil of parsley is one such astringent. How good is it as an astringent? It can be used externally and internally to induce contractions in the gums (which holds teeth stronger), muscles and skin (gives a lift and firmness in the body, a feeling of fitness, and a younger look), hair roots (prevents hair loss) and in the blood vessels (this can slow down or stop hemorrhaging from wounded vessels). Pretty impressive!
May Relieve Flatulence
Gases in the intestine can put you in very embarrassing situations, more so when you are in a party or in a gathering or in a quiet place such as a prayer hall, and the gases start moving inside you making strange noises. The situation grows worse when these gases start to come out. It is left with nowhere. That was only the funny side of it. The darker side of the gases includes troubles like indigestion, flatulence, nausea, vomiting, headaches, stomachaches, chest pains, hypertension, and even the risk of heart attacks (sometimes gases can trigger a heart attack or sometimes a heart attack can be misinterpreted as pain from gas, both ways is dangerous), caused by gases. So, the sooner they are out, the better it is. This can be done with the help of this oil. It does not let the gases form and helps them escape from the body.
May Detoxify Body
Parsley essential oil may promote the removal of toxins and other unwanted substances from the body through the urine. This makes it a detoxifier. This may help keep you safe from many diseases which are born due to the accumulation of these unwanted substances in the body, such as rheumatism, arthritis, boils, skin diseases, and many others.
Can Improve Digestion
The spicy and herbaceous smell of this oil may trigger the appetite and speeds up digestion as well, by increasing the secretion of digestive juices in the stomach. It also makes you feel hungry, which also helps you to psychologically digest the food faster.
May Promote Urination
This property is a contributor to the detoxifying property of this oil. It may increase the frequency and quantity of urination. Animal research published in the American Journal of Clinical and Experimental Urology found that parsley increased urinary volume and urinary pH.
One may wonder how more urination can be beneficial for the body. This may be one of the best ways to remove unwanted substances from the body (excretion is another). It removes unwanted water, salts and toxins like uric acid, fats, pollutants and microbes from the body. By removing toxins and uric acid, it protects you from diseases like rheumatism, arthritis, boils, moles, and acne. By removing water and fat, it helps you lose weight and gives relief to patients of swelling and water-logging. Added to these benefits, the more you urinate, the more calcium and other deposits and microbes are washed away from the kidneys and urinary tracts, thereby protecting you from renal calculi and infections in the urinary system.
Can Act As a Depurative Agent
Depurative means an agent that purifies the blood. This is done in two ways. First, by removing unwanted substances from the blood and cleaning the blood, which this oil does, being a detoxifier, and second, by helping oxygen reach the tissues, which again, this oil may do by stimulating blood circulation since it is a stimulant. 
May Act as an Emmenagogue
Parsley essential oil of parsley has potential emmenagogue property which may make it initiate obstructed or delayed menstruations. It stimulates the secretion of certain hormones like estrogen which help to achieve this. This oil also gives relief from problems associated with menstruation, such as abdominal cramps and pain, nausea, fatigue, and annoyance. These hormones also help bring about puberty and maturity in women and keep their reproductive organs (like the uterus) in good health.
May Reduce Fever
Along with being a depurative, detoxifier and an antimicrobial at the same time, this essential oil is an effective febrifuge, that is, it may reduce fever. How you ask? Let me tell you. Due to its depurative and detoxifying properties, the toxin level may be reduced in the body and this helps get rid of many ailments, including fever, which is sometimes caused due to an increase in the level of toxins in the blood because fever is a reaction of the body to any abnormal insurgence or adverse change in the body. Then, due to its antimicrobial properties, it inhibits microbial infections and this helps get rid of fever caused by microbial or viral actions, such as influenza, yellow fever, typhoid, or malaria.
Can Lower Blood Pressure
Drugs based on narcotics are well known for their hypotensive actions. That is, they instantly lower blood pressure and reduce the risk of a heart attack. These drugs are synthetically derived, so their reaction is fast. However, they have their own adverse effects and in the long run, may give nervous and neurotic problems. The essential oil of parsley may not be that fast, but it is a good choice for regular administration in cases of chronic hypertension and it does not have any adverse effects either. If taken systematically, it helps keep the blood pressure lowered or normal.
May Relieve Constipation
Having clear bowels is a pleasant feeling and those who suffer from constipation know what that is worth. Here is good news for them. The essential oil of parsley comes with laxative properties and may help you get rid of hard and difficult motions, as well as constipation. It may increase the discharge of gastric juices and facilitates the downward motion of excreta by stimulating peristaltic motion in the smooth intestines.
May Stimulate Nerves
Its stimulating effects can be experienced on the whole body. It may stimulate nerves, neurons, the circulation of blood and lymph, digestion, excretion and immune mechanism. Therefore, this essential oil keeps you more active, alert, energetic, strong, and safe.
May Protect Stomach
Parsley essential oil takes care of the stomach, the power generator of our body. It may soothe it, maintains proper flow of gastric juices into it, reduces inflammations in it, protects it from infections and helps heal wounds and ulcers.
May Improve Uterine Health
This property is an outcome of its property of promoting secretions of certain hormones like estrogen and progesterone. These feminine hormones maintain uterine health by regulating menses and protecting it from other problems of the uterus like uterine ulcers and dryness.
Parsley essential oil is also found to be effective in curing many other problems such as blood vessel rupture, cellulite, sciatica, colic, hemorrhoids, amenorrhea, cystitis, and loss of libido.
A Few Words of Caution: Parsley essential oil shows moderate toxicity, particularly towards the liver and has certain non-sensitizing effects. It also has abortifacient and emmenagogue properties, so it should not be used during pregnancy.
Blending: The essential oil of parsley forms fine blends with the essential oils of clary sage, orange, rose, tea tree and ylang-ylang.