Using essential oils (EOs) neat on the skin seems to be a growing practice in the general public. ("Neat" means not diluted) There are more and more reports of serious reactions to this practice, however. Reputable sources recommend diluting EOs before using them on the skin, but the dilution rates recommended by various authorities are not consistent.
The Tisserand Institute recently issued general guidelines for diluting most EOs -- see table below. Not all EOs are generally regarded as safe (GRAS), so use these guidelines with care. Tisserand's book "Essential Oil Safety" is a good resource for science based information about a wide variety of EOs.
Two EOs that require special caution are cassia EO and cinnamon bark EO. The Tisserand Institute has issued a warning that both EOs are highly likely to trigger dermatitis and allergic reactions when used on the skin. The Institute recommends using them at no higher than 0.1% in skin products, if they must be used at all. (That's a maximum of 1 gram of EO per 1000 grams of product)
Source: http://tisserandinstitute.org/new-survey-reveals-dangers-of-not-diluting-essential-oils/
The Tisserand Institute recently issued general guidelines for diluting most EOs -- see table below. Not all EOs are generally regarded as safe (GRAS), so use these guidelines with care. Tisserand's book "Essential Oil Safety" is a good resource for science based information about a wide variety of EOs.
Two EOs that require special caution are cassia EO and cinnamon bark EO. The Tisserand Institute has issued a warning that both EOs are highly likely to trigger dermatitis and allergic reactions when used on the skin. The Institute recommends using them at no higher than 0.1% in skin products, if they must be used at all. (That's a maximum of 1 gram of EO per 1000 grams of product)
Source: http://tisserandinstitute.org/new-survey-reveals-dangers-of-not-diluting-essential-oils/