How to make your own herb-infused base oils
Introduction
Herbs have been infused in oil to extract their medicinal benefits since antiquity. The earliest records of oil infusion came from the Ancient Egyptians, Greeks & Romans. They used these oils medicinally, cosmetically and for culinary purposes.
Simply put, an infused oil is a made from a base oil. These oils are infused (macerated) with fresh dried or powdered plant material over a period of time. Infusions often require a heat source to maximise the process. The plant material is then filtered out and the resulting oil is bottled, ready for use.
Mastering the art and craft of making infused oils will enable you to create a variety of personal care, therapeutic and culinary products to your own specification. Base oils (infused or otherwise) are the foundation of many skin and hair products. They are used in massage oils, creams (emulsions) for face, hair and body, ointments, hair masks, cleansers, lotions, shampoo, soap, sugar scrubs, hot oil treatments and candles.
Olive oil can be infused with and carry the nutrients, aroma and flavour of culinary herbs, such as rosemary (Rosmarinus officinalis), sage (Salvia officinalis), mint (Mentha piperita) and thyme (Thymus vulgaris).
What Are Herb Infused Oils?
The base oil used to make ani infused oil acts as a solvent by extracting oil-soluble chemical compounds from the plant material being infused. Typically, this will be the oil-soluble vitamins (A, D, E & K) fatty acids, waxes, resins and any essential oils contained in the plant.
Definition and difference from essential oils
Before we go further, let’s make the important distinction between base oils and essential oils (also known as volatile or aromatic oils). Essential oils are distilled from aromatic plants such as Lavender (Lavandula officinalis), Tea-tree (Melaleuca alternifolia) and Peppermint (Mentha piperita). Essential oils are potent, highly concentrated and used in very small quantities (drops). They should not be used unless diluted, although there are some exceptions such as Lavender and Tea tree. Essential oils are often added to base oils to enhance their overall therapeutic effect. Other examples of essential oils are Eucalyptus (Eucalyptus globulus). Thyme (Thymus vulgaris) Cedarwood (Cedrus atlantica) and Sweet Birch (Betula lenta).
Choosing the Right Base Oil
Base oils are also known as fixed oils, carrier oils and vegetable oils. Base oils can be extracted from various parts of a plant, such as the fruit, nut, seed or leaf. For example, olive oil is extracted by cold pressing the olive fruit. Unlike essential oils (except for the few exceptions mentioned) base oils are safe to apply undiluted, to skin.
Base oils are also derived from animal sources such as lard, tallow and fish oils. Mineral oils are also base oils. For example, paraffin oil and white oil are made from petroleum and crude oil, respectively. Please note that these oils are not suitable for making oil infusions!
Base oils can be used alone or blended with other base oils. Each oil has its own unique characteristics. Understanding the variations is important, as it will influence the outcome of your final product. There are two types of base oils, long oils and short oils. These terms indicate how well and how quickly the oil is absorbed into the skin.
Long oils are so called because their ability to be absorbed into the skin and the pace at which they do so ranges from poor to average. An example of this is Grapeseed oil. These characteristics make the oil very useful in massage therapy, as it allows for plenty of “rubbing time”, without the masseuse having to stop frequently to reapply the oil. Grapeseed oil is also very useful as a facial cleanser because it allows time for the oil to linger on the surface of the skin, while it picks up grease, dirt and grime.
Castor oil (Ricinis communis) is another example of a long oil. Its ability to absorb is poor as is the rate (speed) of absorption into the skin. I always use this oil as an ingredient in my cleansing cream, because it remains on the skin long enough to absorb impurities. I never use it to infuse oils. I have tried, but it is very reluctant to absorb, does not extract the medicinal benefits from the herbs very well, so cannot deliver these benefits to the skin.
Olive oil (Olea europaea) is also a long oil. In skincare, it is a good choice for making ointments and barrier creams (i.e. for nappy rash). Barrier creams act as a buffer by protecting the skin from friction.
Coconut oil (Cocos nucifera) is also in this category. Base oils are not usually solid, but coconut oil is one such example. Solid oils contain a high volume of stearic fatty acid, which can be removed to make the oil more liquid. The liquid form of coconut oil is referred to as fractionated coconut oil.
On the other hand, short oils (also known as on-and-gone oils) are absorbed into the skin very quickly and thoroughly leaving no greasy residue. I only use short oils for making oil infusions, as they are perfectly suited to this purpose. Short oils are able to absorb and transfer the therapeutic benefits of the plants by penetrating the epidermis (outer layer of the skin). Examples of short oils are Jojoba oil, (Simmondsia chinensis) and Avocado oil (Persea gratissima). These oils make excellent moisturisers, because they require little rubbing to achieve total absorption. Technically, Jojoba oil is a wax, but it can be used like any other short oil.
Whatever you choose, make sure you use a good quality oil from a reputable brand.
In addition to the choices between long and short oils, there are oils that have a higher tolerance to heat than others and I believe these are a better choice for making infusions.
Base oils with a degree of heat tolerance
Short oils
Avocado (Persea gratissima)
Hazelnut (Corylus avellana) not to be used by those with nut allergies
Jojoba (Simmondsia chinensis)
Macadamia nut (Macadamia ternifolia) not to be used by those with nut allergies
Rice bran (Oryza sativa)
Sesame (Sesamum indicum)
Long oils
Sweet almond oil (Prunus Amygdalus Dulcis)
Peach kernel oil (Prunus Persica)
Best Herbs to Use for Oil Infusion
There is a plethora of herbs that can used to make an oil infusion. It really depends on what you want to use it for, but here are some well-known herbs with healing properties.
The quality of your herbal infused oils is only as good as the quality of your ingredients. Only use dried plant material that has retained its colour, odour and is pesticide-free. Do not use herbs that crumble to dust when you handle them. They are way past their best and no longer retain any therapeutic qualities.
St. John’s Wort (Hypericum perforatum) is often used to make a healing ointment. St. John’s wort is a valuable remedy for burns, including sunburn, bruising and wound healing.
Lavender (Lavendula officinalis) oil is perfect for calming anti-inflammatory action. It has antiseptic properties and can also be used for the relief of mild burns. The rich volatile oil content aids the relief of muscular aches and pains. Headaches, cuts, sores and varicose ulcers will also benefit from an application of this oil. It can be made into a facial cream to relieve eczema and acne.
Marigold (Calendula officinalis) is anti-viral, anti-fungal and anti-bacterial. I use it to help wound healing and in cases of eczema, acne or psoriasis. Marigold is great used in creams for burns, cold sores, sunburn, bee stings, insect bites, rashes and dry itchy skin.
Comfrey Leaf (Symphytum officinalis) promotes wound healing by promoting the growth of epithelial cells and is often used to prevent scar formation following wound healing. Note: Comfrey has no antiseptic qualities, so must not be used until infection has been cleared, as it can seal up the wound trapping the infection.
Herbal hair care
There are a number of 
Ayurvedic herbs that can be infused to promote hair growth and deal with issues such as alopecia and thinning hair. Amla (Phyllanthus emblica) is considered to be the most potent of these herbs, but these others are worth investigating Bhringraj (Eclipta prostrata), Brahmi (Bacopa monnieri) and Shankhpushpi (Convolvulus prostrates) are just a few.
Methods for Making Herb-Infused Oils
There are several methods that can be used to make infused oils. The chosen method will largely depend on the plant material you are using and the heat tolerance of your oil.
Step-by-Step Guide (General Instructions)
There are several ways that you can make oil infusions. I will be using the folk method throughout. This is a traditional method which does not use measurements of herbs or oil, but approximations only. I don’t think that specific measurements work, because each herb varies in the amount of oil it is able to absorb. The length of time it will take to infuse your oil you will depend on the method you use. First, let’s take a look at the equipment you will need:
Equipment
Depending on your chosen method of infusion, you will need one of the following: Bain-marie also known as a porringer or water-bath, crock pot, yoghurt maker or dehydrator, access to an airing cupboard.
For all infusion methods you will need all these supplies
- Glass jar with a tight-fitting lid for infusing (macerating) your oils.
- Muslin, finely woven cheesecloth, coffee filter or reusable nylon mesh bags.
- Parchment paper
- Large sieve
- Glass bowl
- Plant material (root, rhizomes, leaves, flower heads, seeds, stems).
- Herb grinder or coffee grinder. (except for powdered herbs).
- Spoon (metal or wooden)
- Base / fixed oil
- Dark glass bottle
- Thermometer
- Labels
- Natural Vitamin E oil (d-alpha tocopherol). Note: This should be added to your base oil before (optional).
Preparation
These are instructions for preparing your oils prior to infusion regardless of the method you are using.
Dried herb: Place your plant material into an herb/coffee grinder. Mill until the material is reduced in size (you do not need to reduce it to a powder). Grinding the herb beforehand increases the surface area and produces a more potent infused oil.
Fresh herb: First allow your fresh plant material to wilt and lose some of its water content by covering it with a cloth and leaving it out on your kitchen counter top for about 12 hours. Once wilted chop the herb fairly coarsely with a sharp knife.
General instructions for both fresh and dried herbs.
- Fill a wide-necked glass jar three-quarters full with your chopped herb. Do not pack the herbs too tightly, allow them space to breathe.
2. Pour enough oil to completely cover the herb. Always leave a 2.5 cm gap at the top of the jar. Dried plant material may expand and soak up the oil, leaving the plant material exposed. Stir the jar to disperse any air pockets. Top up with more oil if needed, ensuring the herb is fully submerged in the oil.
3. Place a piece of parchment paper over the top of the jar and put the lid on. Make sure the lid fits snugly.
Method of Infusion
You will see specific instructions under the infusion method you have chosen.
Decanting
- After the specified infusion time carefully remove your jar from its heat source and remove the lid.
- Allow it to cool and strain the contents through a sieve, lined with a piece of muslin, cheesecloth, nylon mesh bag or coffee filter into a jug placed underneath.
- At this stage (especially for fresh herb infusions), it is important to let the infused oil sit in the jug for at least a few hours to allow any impurities to settle at the bottom of the jug. Pour off the oil, taking care to leave any unwanted debris behind. Before bottling, the oil can be left to sit for a few more hours to ensure all the impurities have been removed.
- If the filtered oil appears cloudy after this process, this is an indication that water is present. To remedy this, heat the oil gently (70°C for 20 minutes) until the residual water has
- Pour your filtered infused oil into a clean, dry dark glass bottle. Dark glass protects the oil from light and heat, extending their shelf-life.
- Label your finished product. Include the type of oil and herb used and the date of bottling
Keep your oil in a cool, dark place. The fridge is ideal.
Cold Infusion Method
This age-old method requires low, stable ambient temperatures of approx. 25 to 30°C / 77 to 86°F, which is perfect for a long, slow infusion. I think it is one of the best methods because of the length of time the oil has to draw out the therapeutic components of the plant material. However, this is not an ideal method if you need your infused oil quickly, with infusion times between 4 to 6 weeks, but it will be worth the wait! An airing cupboard is the ideal location for this method. I place my jar of herbs and oil right next to the hot water tank alongside my home-made ferments, sauerkraut, vinegar and kefir.
Prepare your oil for infusion, as instructed. Make sure to check your oil every other day and give it a good stir until it’s ready to decant. Both fresh and dried herbs can be infused in this way. Don’t be afraid to use fresh herbs (wilt in advance). Regularly checking your batch will allow you to see if there is a need to siphon off any water that has seeped into the oil from fresh plant material. Decant after 4-6 weeks. Leave tough plant parts to infuse for the full 6 weeks. Decant your infusion, as instructed.
Sunlight or Solar Infusion
The sun infusion method is best for fresh (wilt in advance) or dried, lightweight plant material with low levels of water or mucilage. Some examples of herbs suited to this method are Mullein flowers (Verbascum Thapsus), Lemon Balm leaves (Melissa officinalis), Marigold petals (Calendula officinalis) and the aerial parts of St. John’s Wort (Hypericum perforatum).
Prepare your infusion. The jar should be sealed and left on a sunny windowsill for 1-2 weeks. The length of time depends on the heat of the sun. In strong sunlight a week is sufficient, otherwise leave it for 2 weeks. Shake the jar daily to aid the infusion process. Decant your infusion.
Heat Infusion Method
There are a few options to choose from when infusing herbs with heat.
Water Bath Method
A water bath is also known as a double boiler, bain-marie or porringer. Note: Avoid aluminium cookware. Aluminium can leach into food. Stainless steel is a good option. This is one of the quickest ways to make an infused oil and is especially suited for tough plant material such as dried roots, rhizomes, bark, thick leaves, tough stems and seeds. Either dried or fresh herbs (wilt in advance) can be used.
Prepare your infusion, as instructed. This method is a little different from the others, because your herb/oil mixture goes directly into the inner container to infuse and not in the jar. The inner container sits inside the outer container which contains water, placed on the hob to simmer. Ensure there is enough water in the outer container so that it touches the base of the inner container. The oil should cover the herb by about 2cm. Put the pan on the hob and gently simmer for an hour. Do not allow the temperature to get too high, around 120 to 140°F is ideal. Decant your oil, as instructed.
Dehydrator / Yoghurt maker Method
For both methods prepare your infusion, as instructed and place the covered jars into the dehydrator or yoghurt maker.
The temperature for both methods of infusion is controlled by thermostat. A yoghurt maker can be set to a temperature of 90°F / 32°C over a period of 24-48 hours for a long, slow infusion. A dehydrator (I use the Excalibur) has a temperature range of 85°F to 165°F / 35°C to 74°C). I use this method fairly often and have made several high-quality infused oils in about 24 hours at a temperature of 120°F / 49°C Decant your infusion, as instructed.
Slow Cooker (Crock pot) Method
This is another fairly quick method of producing infused oils. Prepare your infusion as instructed. Fill the crockpot with enough water to just sit beneath the rim of the jar. Put a lid on your jar and place it in the crockpot on top of a tea towel. Turn the crockpot onto a low setting and leave it uncovered. You should aim to keep the water temperature at about 120 – 140°F. Use a thermometer to check the temperature periodically. Infusion times can be up to 24 hours. The tougher the plant material, the longer the infusion time needed, so use your discretion. Decant your oil, as instructed.
How to Store and Preserve Herb Infused Oils
Once you have decanted your oil as instructed above. You will need to store it in a cool away from sunlight and heat in a tightly sealed dark glass bottle that should be completely dry. The fridge or freezer is ideal. The oil will keep in these conditions for about a year. Adding Vitamin E
oil (1% of the total weight of your infused oil) will extend the shelf life of your product.
Fluctuations in temperature can also turn oils rancid, so keep the temperature cool and constant. Fill the bottles to the brim to exclude air and reduce oxidation as much as possible. Take all of these precautions to prevent your oil from turning rancid.
Safety Tips and Precautions
Rancidity and its causes
The presence of water or mucilage in your infused oil can cause it to turn rancid. Rancid oils should be discarded. Rancidity is caused by the breakdown of fats and oils into fatty acids. This breakdown is caused by reactions with oxygen, light, heat (including fluctuations in temperature), moisture and the passage of time. Rancidity can also be caused by the presence of mould, yeast or bacteria.
Frequently Asked Questions (FAQ)
Can you leave herbs in infused oil?
There is no advantage to leaving the herb (whether dried or fresh) in the oil after the infusion period. At that point, all the nutritional benefits of the herb have been absorbed by the oil. In the interests of hygiene and safety it would be best to remove the used plant material.
Is it better to use fresh or dried herbs?
Fresh oils are usually preferable, as their therapeutic activity is more potent than dried herbs.
How do you infuse oils with herbs in oven?
Personally, I do not recommend that herbs be infused this way. Even the lowest oven temperature (70°C / 170°F) would be too high for heat-sensitive oils.
I do hope that you find this information useful and feel inspired to make your own infused oils.
I teach herbal pharmacy workshops in South London, so please do drop me a line if you are interested.