In general, essential oils are safe to use in the home. However, because of the high concentration and potency of the oils it is necessary to take some precautions into account, as you would with any other household item.

Always check the specific safety data before using a new oil.

Do not use essential oils internally. This rule is in accordance with the safety guidelines recommended by the Federation of Aromatherapists. Essential oils do not mix with water, and in an undiluted form they may damage the delicate lining of the digestive tract. In addition, some essential oils are toxic if taken internally.

Neat application. In general, essential oils should not be applied neat to the skin – always dilute them in a carrier oil or cream first. There are exceptions to this rule, such as the use of neat lavender for cuts, spots, burns etc. Certain non-irritant essential oils, such as ylang ylang or sandalwood, may be applied neat to the skin as perfumes. Always do a patch test first, and keep well away from the eyes.

Skin irritation. Oils which may irritate the skin or cause an allergic reaction are sweet basil, black pepper, cinnamon leaf, clove bud, eucalyptus, ginger, lemon, lemongrass, peppermint, pine needle and thyme. These oils should be used in half the usual recommended dilutions and no more than 3 drops added to the bath. If irritation does occur, bathe the area with cold water

Sensitive skin. Some oils, including tea tree, may cause skin irritation in people with very sensitive skins. Since tea tree is such a useful oil and may sometimes be used neat , it is important for those with sensitive skins to dilute it first in a non-oily cream or gel. Always do a patch test before using a new oil to check personal sensitisation.

Patch test. Before applying any new oil to the skin, even as a perfume, always do a patch test. Simply put a few drops on the back of your wrist, cover with a plaster, and leave for an hour or more. If redness or irritation occurs, bathe the area with cold water. For future use, reduce the concentration level by half or avoid the oil altogether.

Toxicity. Essential oils which should be used in moderation externally because of high toxicity levels are aniseed, camphor, clove bud, eucalyptus, hyssop, nutmeg, oregano, sweet fennel and spanish sage.
Hazardous oils such as pennyroyal, mustard, sassafras, rue and mugwort should not be used at all.

Phototoxicity. Some oils are phototoxic, which means they cause skin pigmentation if exposed to direct sunlight. Do not use the following oils on the skin, either neat or in dilution, if the area will be exposed to the sun or ultra-violet light (as on a sunbed): bergamont (except bergapten-free oil), cumin, lemon, lime or orange.

Babies and children. Always dilute oils for babies and infants to at least half the recommended amount. For young children, avoid altogether the possibly toxic and irritant oils listed above.
Babies 0-12 months: use only 1 drop of lavender, rose, roman/german chamomile, neroli or mandarin essential oil, diluted in 1 teaspoonful carrier oil for massage or bathing.Infants 1-5 years: use only 2-3 drops of the ‘safe’ oils – non-toxic and non-irritant.Children 6-12 years: use as for adults but in half the stated concentration.
Teenagers: use as directed for adults.

Pregnancy. During pregnancy, use essential oils in half the usual stated amount because of the sensitivity of the growing foetus. Oils which are potentially toxic or have emmenagogue properties(that is they stimulate the uterus muscles) are contra-indicated.
The following oils should be avoided altogether: basil, cinnamon leaf, citronella, clary sage, clove, hyssop, juniper, marjoram, myrrh, spanish sage, tarragon and thyme.
The following oils are best avoided during the first four months of pregnancy: atlas cedarwood, peppermint, rosemary and sweet fennel.

High blood pressure. Avoid the following oils in cases of this condition as they can raise the blood pressure: hyssop, rosemary, sage (all types) and thyme.

Epilepsy. Avoid the following oils in cases of epilepsy because they have a powerful effect on the nervous system: sweet fennel, hyssop and sage (all types).

Alcohol. The oil of clary sage should not be used in any form within a few hours of drinking alcohol. It can cause nausea and exaggerated drunkenness.

Homeopathy. Homeopathic treatment is not compatible with the following oils due to their strength: black pepper, camphor, eucalyptus and peppermint.

Storage. Store in dark bottles, away from light and heat, and well out of the reach of children.