Use and Dosage

In aromatherapy - specially in clinical - the dosage of ingredients plays an important role for the effectiveness of blends and for ensuring the safe use of essential oils. 
In most recipes the quantity of blending oils is given in ml or oz (fluid ounce) while the quantity of essential oils is given in drops. The addition of essential oils in blends is simple since most providers are using euro dropper bottles for safety reasons. For measuring blending oils or creams I believe you will find the special measuring spoons or cups very useful. In general the correlation of volume units used in aromatherapy and the spoons used in a common kitchen is the following:

5 ml (0,16 fl oz)   ~ 1 teaspoon
10 ml (0,33 fl oz) ~ 1 dessertspoon
15 ml (0,5 fl oz)   ~ 1 tablespoon

It is also useful to know that:

1 fl oz = 30 ml and
1 ml of essential oil ~ 20 (metric) drops.

There are many methods for using the blends prepared in aromatherapy. In general the proportion of ingredients in a recipe should not be altered, since it is important for the synergistic action of essential oils.  However, if it is required to use fewer quantities of essential oils it is advisable to halve the number of drops in the blends while keeping to the correct proportions and using the same amount of base oil specified. In such a case it may be required to use the blend more often and for a longer period of time in order to achieve the desired effects.
The methods of use and suggested dosages of essential oils mentioned below are from the book "The Fragrant Mind", written by the internationally acknowledged leading aromatherapist Valerie Ann Worwood:

Dosage: maximum 8 drops.
Method: fill the tub with warm water and add the essential oils. You can mix them with a small quantity of base oil so they dilute better in water. Stay in the tub for at least 10 minutes inhaling deeply. Keep the bathroom door closed so the vapours do not escape. Unless otherwise indicated avoid using the following essential oils in a bath:  basil, cinnamon, clove, peppermint, thyme, ginger and eucalyptus.

Dosage: maximum 2 drops.
Method: wash as usual and then add the essential oil drops on a wet sponge. Rub your body while standing under the warm water, inhaling deeply through the nose.

Dosage: 3 drops per person.
Method: same as for bath.

Dosage: 2 drops per 600 ml water.
Method: mix the essential oils with the water and place them on the heat source. Suggested essential oils: eucalyptus, teatree and pine.

Dosage: maximum 1 drop per 1 ml base oil.
Method: if you are using more than one essential oil mix them first in a bottle and then add the base oil. Turn the bottle upside down a few times and roll it between your hands so the blend becomes warm. For a female body massage 20 ml of base oil are usually adequate.

Tissue or handkerchief 
Dosage: 1 drop
Method: drip the essential oil on the tissue or handkerchief and inhale deeply whenever you feel the need.

Vapour inhalations
Dosage: maximum 2-3 drops.
Method: add in a bowl with hot water the essential oils. Place your head above the bowl in a distance of 30 cm and cover it with a towel so the vapours do not escape. Keep your eyes closed and inhale deeply through the nose for about one minute.

Water bowl
Dosage: 1-9 drops.
Method: add in a bowl with hot water the essential oils. Make sure the windows and doors of the room are closed. After 5-10 minutes the essential oils will permeate atmoshpere. Replenish if required but the aroma should not be very strong.

Oil burners and diffusers
Dosage: 1-6 drops.
Method: fill the bowl of the oil burner or diffuser with water and add essential oils. When the aroma weakens add essential oils. When using this method make sure you check often the quantity of water in the bowl while the appliance is on.

Dosage: 1-9 drops.
Method: drip the essential oil on a cotton cloth and place it on the radiator while it is working.

Dosage: 1-9 drops.
Method: add the essential oils in the water of the humidifier.

Room spray
Dosage: minimum 4 drops per 280 ml water.
Method: fill a sprayer with warm water and add essential oils. Shake well and spray high in the air. Avoid spraying over wooden or other vulnerable surfaces.

Log fires
Dosage: maximum 3 drops.
Method: drip the essential oils on the logs about half an hour prior to lighting the fire.Suggested essential oils: cypress, sandalwood and cedarwood.

Silk or paper flowers
Dosage: 1 drop per flower.
Method: drip the essential oils on the petals or stem of the flowers and place them into a vase. Essential oils evaporate and usually they do not stain. However some essential oils have a slight colour and you should be careful when using this method.

Dosage: 1-3 drops per pillow.
Method: essential oils usually do not leave stains so you can directly drip them on the pillow. Alternatively you could drip them on a pillow corner or on a cotton cloth which you will then place inside the pillowcase or underneath the pillow.

Dosage: 1-2 drops.
Method: put the essential oils on the sleeve or colar. Essential oils evaporate and usually they do not stain. However some essential oils have a slight colour and you should be careful when using this method.

Dosage: for 100 ml perfume add 33 ml essential oils and 66 ml jojoba oil or vodka. If you are using vodka you can further dilute the blend in 50% water.
Method: Blend in a glass perfume bottle the essential oils with jojoba oil or vodka according to the above proportion. Spray on the base of your neck and on your wrists or inhale directly from the bottle.

Dosage: -
Method: due to the rising interest in aromatherapy manufacturers make special bottles and pendants or bracelets in which you can put essential oils or perfume and enjoy their beneficial properties the whole day.

Dosage: 10-15 drops per 50 ml.
Method: add essential oils in pre-packaged, perfume free creams or in the creams and lotions you will make on your own.