Once upon a time in Croatia, people were afraid to use oral preparations of essential oils. Today, everything is different. We realized that oral medications and dietary supplements with essential oils have been around for decades. Dose, optimal ratio of efficacy and good tolerability and reduced possibility of irritation of the digestive system, all these are the characteristics of a quality oral preparation. Some preparations are simple, like honey mixtures, but are reserved for safe and non-irritating essential oils. Never put oregano in a honey mixture, at least not in a larger dose, but in a capsule – yes.
Oral preparations are the domain of completely professional aromatherapy, since the possibility of side effects increases with oral administration. In Croatia, once a boogie man, today this method is much more used. Oral application of essential oils is often the one that makes the difference between Anglo-Saxon and French schools of aromatherapy. Oral preparations vary in ease of preparation from relatively undemanding formulations (such as honey mixtures) to very demanding (such as capsules). Here’s a warning: Don’t take essential oils orally without having enough knowledge about them!
Essential oils “on sugar”
Essential oils, similar to propolis tinctures, can be taken with the help of sugar. Two to four drops of essential oils are put on a little bit of (brown) sugar or fructose, placed on the tongue and then drunk with a glass of water. This simplest way is limited to oils that do not irritate the mucous membrane of the mouth, and have a pleasant taste. These two conditions create a relatively narrow set of essential oils: fennel, anise, cumin, peppermint, orange, lemon and mandarin peel, ginger and similar oils. Essential oils on sugar do NOT protect the mucous membranes of the mouth and oesophagus from the effects of the essential oil, so this method of application is absolutely not suitable for some very useful essential oils such as oregano or clove.
Medicinal honeys have a great tradition in Croatia and throughout Europe, but their most useful application is for infections of the upper respiratory system. Namely, honey itself coats the mucous membrane, acts as an “osmotic shock” for bacteria and reduces their number in a short time. They are obtained by vigorously mixing essential oils with honey. It is dispersed into tiny droplets (essential oils do not melt in honey), and the very viscosity of honey prevents the separation of phases. Due to its sweet taste, honey is suitable for making oral preparations, but only those oils that are safe for oral use, and those that do not have an aggressive or very unpleasant taste, just as in the case of essential oils “on sugar”.
The usual dose is two drops of essential oil per teaspoon, which means adding 2 drops to 10-12g of honey. Some view honey in the context of honey mixture as a carrier that allows the healing effect of essential oil, and those who are better acquainted with different types of honey, can take advantage of the synergistic effect. For example, rosemary honey will be more suitable for honey mixtures for the digestive system, while sage honey will be more suitable for honey mixture used for respiratory problems.
In addition to honey, honey mixtures is also made with cereal malts.
Alcoholic solutions of essential oils
All essential oils dissolve well in 90% ethanol. Today, this method of application has slowly become part of the history of pharmacy and aromatherapy, in the era before the formulation of oleocapsules. One of the most famous magistral preparations was an alcoholic solution of anise essential oil. A 10% solution of anise in 90% ethanol would be made. Then 20-30 drops would be dropped into a glass of lukewarm water and stirred immediately. A relatively unstable suspension of the essential oil in the drinking water would result. This solution was used to treat indigestion such as bloating.
But an extremely small number of essential oils can be applied in this way, so oleocapsules are a better solution than such archaic formulations.
Since essential oils do not dissolve in water, there are several ways that oils can be dissolved in water, most commonly with the help of emulsifiers. These emulsifiers must be approved for oral use, and classic cosmetic emulsifiers are not used. In France, many decades ago, emulsion bases for oral use under the trade name Disper and Solubol were developed, based on the food emulsifier lecithin. Disper contains lecithin, ethanol, sweet almond extract, oleic acid and vitamins E and C. Solubol is a non-alcoholic type of emulsion base and contains, in addition to lecithin, glycerin, coconut oil, maltodextrin, and acacia gel. The method of use is relatively simple. 2 drops of essential oil are mixed with 8 drops of Solubol, mixed with 20mL of water and drunk.
Aqueous emulsions are less irritating than taking essential oils “on sugar” or in honey mixtures, because essential oils are emulsified and less absorbed in the mouth and oesophagus. However, they are not good for taking larger amounts of oil (over 2-3 drops) or for irritating oils.
Capsules are the most professional form of oral formulations of essential oils, suitable for higher doses, irritating oils and oils with an unpleasant taste. Capsules are known from classical medicine; these are small hollow cylindrical dosage forms that hold a certain amount of drug substances. Capsules can be gelatinous and in pharmacy they are the most common and cheapest. In food and medicine supplements, due to vegans or religious groups that do not use pork gelatine, the following are created:
- Cellulose capsules, i.e. from hydroxypropyl-methyl cellulose, so-called HPMC capsules. The most known type of such capsule is the Vcaps HPMC capsule from Capsugel. They have special V-shaped grooves that allow better capsule closure and less oxygen penetration into the capsule. They are vegan certified, as well as Kosher and Halal certified. They usually come in two colours, transparent without pigments, and white painted with titanium dioxide, although there is a whole panel of colours at the request of customers. The great advantage of cellulose capsules is that they do not react with aldehydes, unlike gelatine capsules, which is important to us in aromatherapy because of the aldehydes present in some essential oils. You can find brochures for Vcaps and Vcaps Plus capsules.
- Pullulan capsules are not made of cellulose derivatives, but exclusively of fermented starch, tapioca. Tapioca is derived from the cassava plant (Manihot esculenta) and is a traditional food plant of South America. They have the advantage of a higher gloss, and an extremely “green” way of obtaining without the use of unnecessary chemistry.
- OceanCaps are not vegan capsules because they are made from fish gelatine. They are aesthetically very acceptable, extremely transparent and are used by some manufacturers for food supplements.
According to the type of carrier, the excipient that binds the essential oils, capsules can be formulated as:
- Capsules with powdered carriers made by trituration (mixing) of powdered carrier and essential oil. The essential oil is adsorbed on a powder carrier and the mixture is filled into capsules. Vcaps and pullulan capsules are ideal for filling with this type of carrier. The most common carriers are dibasic calcium phosphate, sorbitol, but they can also be clays such as kaolin, and zeolite. Highly dispersive silicon dioxide (aerosil) is often added to the capsules, for better rheological properties (leakage properties), and as a substance that protects against moisture. When choosing a carrier, one should pay attention to incompatibilities, i.e. the possibility that the essential oil reacts with the carrier. An example of this is the essential oil of anise and fennel, rich in trans-anethole, which react with zeolites.
- Oleocapsules, where essential oils are dissolved in vegetable oil thus reducing their irritability. Vegetable oils are diverse, sometimes they are just a carrier without much medicinal value, such as oils rapeseed oil, and can also be medicinal vegetable oils such as black cumin oil, evening primrose or borage. Vegetable oils reduce the irritability of essential oils and this is an ideal formulation. Oleocapsules are made as ordinary “soft” gelatine capsules, or in today’s increasingly popular LiCaps capsules. LiCaps are gelatine capsules, but made in the classic form of hard capsules that fuse and thus prevents the contents from escaping the capsules.
After production, the capsules can also be enterically coated. This means that they are coated with a wrapping film of like phthalate hypromellose or shellac, which do not melt in the acidic environment of the stomach, but begin to melt after the duodenum. The most famous such formulation is peppermint essential oil, which is used in irritable bowel syndrome. But the capsules do not have to be enterically coated after production. Some come to market already finished. Examples are HPMC DR capsules by Capsugel, which are very dear to me – they considerably reduce the “burping effect” and are great for people with sensitive stomachs. This is important when applying essential oils rich in phenols (clove, oregano).
The usual dose of essential oil per capsule varies from 50 to 100 mg, sometimes even higher, depending on the purpose of the oil.