Carrier oil, also known as base oil or vegetable oil, is used to dilute essential oil

Essential oil

An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...

s and absolutes before they are applied to the skin in massage

Massage

Massage is the manipulation of superficial and deeper layers of muscle and connective tissue to enhance function, aid in the healing process, and promote relaxation and well-being. The word comes from the French massage "friction of kneading", or from Arabic massa meaning "to touch, feel or handle"...

 and aromatherapy

Aromatherapy

Aromatherapy is a form of alternative medicine that uses volatile plant materials, known as essential oils, and other aromatic compounds for the purpose of altering a person's mind, mood, cognitive function or health....

. They are so named because they carry the essential oil onto the skin. Carrier oils do not contain a concentrated aroma, unlike essential oils, though some, such as olive, have a mild distinctive smell. Neither do they evaporate like essential oils, which are more volatile

Volatility (chemistry)

In chemistry and physics, volatility is the tendency of a substance to vaporize. Volatility is directly related to a substance's vapor pressure. At a given temperature, a substance with higher vapor pressure vaporizes more readily than a substance with a lower vapor pressure.The term is primarily...

. The carrier oils used should be as natural and unadulterated as possible. Organic oils should be used where possible. Cold-pressing and maceration are the two main methods of producing carrier oils. Mineral oil should not be used as it is not absorbed by the skin.

There is a range of different carrier oils, each with a various therapeutic properties. Choosing an oil will depend on the area being massaged, the presenting conditions and the clients sensitivity and requirements.
For massage, viscosity

Viscosity

Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...

 is a major consideration; for example, grapeseed oil is typically very thin, while olive oil is much thicker. Sunflower, sweet almond and grapeseed oils have viscosities midway between these extremes. Carrier oils can be easily blended to combine their properties of viscosity, acceptability, lubrication, absorption, aroma and so forth.

Infused oils are a combination of a carrier oil and plant material and they can be either commercially or domestically prepared. A base oil, often sunflower, is placed in an airtight container with the appropriate plant material for a time. Calendula and carrot oils are produced in this way.

High quality oils sold for culinary use are often eminently suitable for massage use, and are economical; those obtained by cold pressing are preferred. All carrier oils should be kept cool, and away from strong light, to retard rancidification. Rancid oils should be avoided. Refrigerating oils helps preserve their freshness but some oils should not be refirgerated (e.g. avocado). Very cold oils may appear cloudy, but regain their clear state on returning to room temperature. The massage blend should be prepared at the time of treatment, not only because some of the oils have a short shelf life, but also to ensure the treatment is relevant to the clients needs on the day.

Varieties

True carrier oils are generally cold-pressed or macerated vegetable oils taken from, amongst others:

• Sweet almond oil
• Grape seed oil
  Grape seed oil
  Not to be confused with Rapeseed oil.Grape seed oil is a vegetable oil pressed from the seeds of various varieties of Vitis vinifera grapes, an abundant by-product of winemaking.- Cooking :...
  
  
• Avocado oil
  Avocado oil
  Avocado oil is an edible oil pressed from the fruit of the Persea americana . As a food oil, it is used as an ingredient in other dishes, and as a cooking oil. It is also used for lubrication and in cosmetics where it is valued for its regenerative and moisturizing properties.It has an unusually...
  
  
• Olive oil
  Olive oil
  Olive oil is an oil obtained from the olive , a traditional tree crop of the Mediterranean Basin. It is commonly used in cooking, cosmetics, pharmaceuticals, and soaps and as a fuel for traditional oil lamps...
  
  
• Sesame oil
  Sesame oil
  Sesame oil is an edible vegetable oil derived from sesame seeds. Besides being used as a cooking oil in South India, it is often used as a flavor enhancer in Chinese, Japanese, Korean, and to a lesser extent Southeast Asian cuisine.The oil from the nutrient rich seed is popular in alternative...
  
  
• Evening primrose
  Evening Primrose
  Evening Primrose is a musical with a book by James Goldman and lyrics and music by Stephen Sondheim. It is based on a John Collier short story published in the 1951 collection Fancies and Goodnights....
  
  
• Canola (Rapeseed)
• Sunflower oil
  Sunflower oil
  Sunflower oil is the non-volatile oil expressed from sunflower seeds. Sunflower oil is commonly used in food as a frying oil, and in cosmetic formulations as an emollient. Sunflower oil was first industrially produced in 1835 in the Russian Empire.- Composition :Sunflower oil is mainly a...
  
  
• Jojoba oil
  Jojoba oil
  Jojoba oil is the liquid wax produced in the seed of the jojoba plant, a shrub native to southern Arizona, southern California, and northwestern Mexico. The oil makes up approximately 50% of the jojoba seed by weight....
  
  
• Emu oil
  Emu oil
  Emu oil is an oil made from the fat of the emu, Dromaius novaehollandiae, a bird native to Australia.Emu oil and eucalyptus oil have been used historically by the Australian aborigines for the treatment of fevers, coughs, arthritic joints, bruises, cuts and sores.Pure emu oil can vary widely in...
  
  
• Castor oil
  Castor oil
  Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is and its density is 961 kg/m3...
  
  
• Nuts:
  • Walnut oil
    Walnut oil
    Walnut oil is oil extracted from English walnuts . It is about 50% linoleic acid, an essential omega-6 fatty acid. Walnut oil is also a good source of omega-3 fatty acids which are also essential to human nutrition....
    
    
  • Peanut oil
    Peanut oil
    Peanut oil is an organic material oil derived from peanuts, noted to have the aroma and taste of its parent legume....
    
    
  • Pecan oil
    Pecan oil
    Pecan oil is an edible pressed oil extracted from the pecan nut. Like most nut oils, it tastes like the nut from which it was extracted. Pecan oil contains approximately 7% saturated fat, which is less than half the amount contained by olive oil, peanut oil or corn oil...
    
    
  • Macadamia nut
  • Fractionated coconut oil
    Coconut oil
    Coconut oil is an edible oil extracted from the kernel or meat of matured coconuts harvested from the coconut palm . Throughout the tropical world, it has provided the primary source of fat in the diets of millions of people for generations. It has various applications in food, medicine, and industry...
    
    

Sweet almond oil and grapeseed oil are very popular carrier oils.

Safety aspects

Peanut

Peanut

The peanut, or groundnut , is a species in the legume or "bean" family , so it is not a nut. The peanut was probably first cultivated in the valleys of Peru. It is an annual herbaceous plant growing tall...

s are legumes, not "true" nuts, but they share with true nuts the risk of causing allergic reactions, even in minute amounts. Pure peanut and nut-derived oils are not usually allergenic, (as they do not typically contain the proteinaceous part of the plant), but avoiding them may be safer, as serious peanut

Peanut allergy

Peanut allergy is a type of food allergy distinct from nut allergies. It is a type 1 hypersensitivity reaction to dietary substances from peanuts causing an overreaction of the immune system which in a small percentage of people may lead to severe physical symptoms. It is estimated to affect...

 and nut allergy is widespread, oil purity cannot be guaranteed, and other hypoallergenic oils are easily substituted.

If there is any risk of ingestion, mineral oil is best avoided.