Although essential oils are natural products, it is still necessary to follow certain precautions when using them. It is advisable that the public exercises caution and that they consult a qualified aromatherapy practitioner before using aromatherapy for medical use. Essential oils are very concentrated and volatile. Improper use may cause burns, allergic reactions, headache, or nausea. To avoid complications directions should be closely followed and certain safety guidelines should be followed.

• Essential oils are contraindicated in asthma, heart conditions, hypertension, cancer, epilepsy, and frequent allergic reactions.
• Essential oils are contraindicated in pregnancy due to the potential toxicity to the mother and fetus and the risk of triggering spontaneous abortion.
• Avoid using essential oils on babies and children less than 5 years of age. Use aromatherapy on children older than 5 years with caution.
• Essential oils must always be diluted according to the instructions before applying to the skin or using for inhalation.
• Before using an essential oil a simple patch test must be done to ensure it will not irritate the skin. Any reaction will be immediate.
• Toxicity and contraindications for each oil should be well understood.
• Keep essential oils away form eyes and mucous membranes,
• Due to the strong association between smell and memory, special care should be taken when using aromatherapy on patient’s undergoing chemotherapy or feeling very ill. The smell of the oil may induce nausea, vomiting or negative emotions in subsequent context.

• High doses (10-20 ml) of some oils may cause non-lethal toxicity. These include wintergreen, sage, aniseed, thyme, lemongrass, fennel, clove, cinnamon, camphor, and cedarwood.

• Certain oils are more commonly associated with allergic reactions including basil, fennel, lemongrass, rosemary, and verbena oils.