In the short time I've been looking into essential oils and thinking about using them in the topicals that I want to make, I realized that essential oils, like many things found in nature are not always benign. I want to help myself and others, without doing any inadvertent harm in the process. So I'm going to share a little info I've found in the hopes that it will inform and educate anyone who may not of thought about this before, like I was guilty of.
I'm going to share info from the Tisserand Institute mainly in the form of safety charts that are in the public domain. I've repeatedly seen the Tisserand Institute refered to when it comes to safety, so I'm assuming they are a good resource. They also have a book called Essential Oil Safety: A Guide for Health Care Professionals (ISBN-10:0443062412) that is extremely highly rated, but unfortunately out of my price range.
The general safety info is coming from the National Association for Holistic Aromatherapy since their info is brief and concise.
General Safety Guidelines
Check links for footnotes.
General Safety Precautions
Keep all essential oils out of reach of children and pets.
Do not use or recommend the use of photosensitizing essential oils prior to going into a sun tanning booth or the sun. Recommend that the client stay out of the sun or sun tanning booth for at least twenty-four hours after treatment if photosensitizing essential oils were applied to the skin.
Avoid prolonged use of the same essential oils unless they are being used under the guidance of a qualified health professional.
Avoid the use of essential oils you know nothing about on your clients. Research and get to know the oil prior to using it on others.
Avoid the use of undiluted essential oils on the skin, unless otherwise indicated.
If you suspect your client may be sensitive to specific essential oils or if your client has known allergies or sensitivities, it may be wise to perform a skin patch test.
Know the safety data on each essential oil and place into context of use and knowledge.
Use caution when treating a female client who suspects she is pregnant or has been trying to become pregnant.
Keep essential oils away from the eyes.
Essential oils are highly flammable substances and should be kept away from direct contact with flames, such as candles, fire, matches, cigarettes, and gas cookers.
Make sure your treatment room has good ventilation.
Do not use essential oils internally unless properly trained in the safety issues of doing so.
Topical Specific Safety
Dermal Safety
Dermal irritant
A dermal irritant will produce an immediate effect of irritation on the skin. The reaction will be represented on the skin as blotchy or redness, which may be painful to some individuals. The severity of the reaction will depend on the concentration (dilution) applied.
General safety
guidelines include: avoid application of known dermal irritant essential oils on any inflammatory or allergic skin condition; avoid undiluted application; avoid application on open or damaged skin; and dilute known dermal irritants with appropriate vegetable oil or other carrier. If you suspect a client has sensitive skin, perform a skin patch test.
Some examples of dermal irritants include bay, cinnamon bark or leaf, clove bud, citronella, cumin, lemongrass, lemon verbena, oregano, tagetes, and thyme ct. thymol. (This is not a complete list, just examples.)
Dermal sensitization
Dermal sensitization is a type of allergic reaction. It occurs on first exposure to a substance, but on this occasion, the noticeable effect on the skin will be slight or absent. However, subsequent exposure to the same material, or to a similar one with which there is cross-sensitization, produces a severe inflammatory reaction brought about by cells of the immune system (T-lymphocytes). The reaction will be represented on the skin as blotchy or redness, which may be painful to some individuals.
The problem with dermal sensitization is that once it occurs with a specific essential oil the individual is most likely going to be sensitive to it for many years and perhaps for the remainder of his/her life. The best way to prevent sensitization is to avoid known dermal sensitizers and avoid applying the same essential oils every day for lengthy periods of time. Sensitization is, to an extent, unpredictable, as some individuals will be sensitive to a potential allergen and some will not.
The following oils are considered to be dermal sensitizers and are not recommended in aromatic massage (And I would guess topical application since the sticking point is usually with essential oils that will be left on the skin, such as in a topical): Cassia, cinnamon bark, Peru balsam, verbena absolute, tea absolute, turpentine oil, backhousia, inula, and oxidized oils from Pinaceae family (e.g., Pinus and Cupressus species) and Rutaceae family (e.g., citrus oils) Again, only examples, not a complete list.
Photosensitization
An essential oil that exhibits this quality will cause burning or skin pigmentation changes, such as tanning, on exposure to sun or similar light (ultraviolet rays). Reactions can range from a mild color change through to deep weeping burns.
Do not use or recommend the use of photosensitizing essential oils prior to going into a sun tanning booth or the sun. Recommend that the client stay out of the sun or sun tanning booth for at least twenty-four hours after treatment if photosensitizing essential oils were applied to the skin. Certain drugs, such as tetracycline, increase the photosensitivity of the skin, thus increasing the harmful effects of photosensitizing essential oils under the necessary conditions.
Some examples of common oils considered to be photosensitizers are: angelica root, bergamot, cumin, distilled or expressed grapefruit (low risk), expressed lemon, expressed lime, expressed bitter orange, and rue.
There are safe versions that you can find at the link above, but I'm not going to list them here. I think it's better for people to do the research if they are insistent on using one of these oils.
Idiosyncratic irritation or sensitization
Idiosyncratic irritation or sensitization is an uncharacteristic or unusual reaction to a commonly used essential oil. This type of reaction is difficult to predict and rarely occurs but is a possibility.
Mucous membrane irritant
A mucous membrane irritant will produce a heating or drying effect on the mucous membranes of the mouth, eyes, nose, and reproductive organs. It is recommended that mucus membrane irritating essential oils not be used in the bath unless they are adequately diluted in a dispersant such as natural bath gel base, polysorbate or vegetable oil. Bay, clove, cinnamon bark, lemongrass, and thyme ct. thymol essential oils should be avoided in baths completely.
Common mucous membrane irritant oils include but are not limited to, bay, caraway, cinnamon bark or leaf, clove bud or leaf, lemongrass, peppermint, and thyme ct. thymol.
So with this information I feel that I have to be careful with the others that I'm trying to help. I've already been in contact with my people to have conversations about allergies, and previous reactions to essential oil, possible interactions with prescription medications, and speaking with their medical professionals about the blend that we come up with for their particular malady to ensure there are no contraindications with medications as there are some essential oils/carrier oils that can effect prescribed medications. We also are going to be doing a couple skin patch tests, just to avoid any unpleasantries.
I hope some of this will be interesting or beneficial to a few. Next I'm planning on posting on dosage, as this is our safety net when it comes to topicals and essential oils.
Cheers.
) so there’s a still a lot to be learned, but yes there is some THC interaction at CB2 receptors.
And you’re still fairly new so, 
to 420 Magazine!
. Let me do a bit of digging and get back to you if no one else gets here first!