Most essential oils are safe to use in the bath, massage and inhalation where the dosage is low. The following comments do not apply to oral ingestion where you should know the chemical properties and the appropriate dosage of the oils you ingest. Above all treat these precious essences with the respect they deserve.
Three issues to be aware of are:
There are a few oils that react with the UV rays of the sun or a tanning bed and can cause a severe burn or leave a permanent mark on the skin when used immediately before spending prolonged time in the hot sun or tanning in a salon. Provided they are kept at a low dilution in a blend they are fine to use at other times. The effects of the oil can last up to 12 hours.
These oils include angelica root, bergamot, grapefruit, lemon, lime, bitter orange and lemon verbena.
Most essential oils won’t cause any allergic reaction but some oils like geranium, palmarosa, benzoin and cinnamon bark have the possibility of doing so in people who have a history of eczema, asthma and other allergies.
In that case it is best to do a patch test first. Put a drop or two of the essential oil either neat or blended 10% in a vegetable oil on the inner arm and cover with a band aid. If there is no reddening of the skin and/or itching after 24 to 48 hours the oil is probably safe to use. Sometimes sensitivity develops over time. If so discontinue use.
Sometimes if too much essential oil or those known to cause irritation are used the skin may become itchy, red, sore or develop a rash. Remove the oil from the skin, apply a bland vegetable oil, remove and repeat a few times. Oils that can have skin irritating properties are cinnamon bark, oregano and clove.
If essential oil gets into your eyes immediately flush with a vegetable oil and wipe off the excess. If irritation continues seek medical advice.
Finally keep all essential oils out of reach of young children.