What is it?
An essential oil from the fruit of the lime, Citrus aurantifolia. It is either cold-pressed from the peel or distilled, and the two types differ in one important way: pressed lime oil contains furocoumarins that can cause sunburn-like skin reactions in sunlight, while distilled lime oil does not. Lime oil scents cosmetics and personal care products and flavors foods.
Key information
- Cold-pressed lime oil is phototoxic, and IFRA limits it to 0.7 percent in leave-on skin products, with no limit for rinse-off products.
- Distilled lime oil caused no phototoxic reactions in the animal and human tests reviewed by the CIR Expert Panel.
- The CIR Expert Panel concluded in 2014 that citrus peel oils, including lime, are safe in cosmetics when leave-on products contain no more than 15 ppm bergapten and are formulated to be non-sensitizing and non-irritating.
- Lime oil is generally recognized as safe (GRAS) by the FDA as a food ingredient.
More information
Like other citrus oils, lime oil is largely made of monoterpenes such as limonene, with aldehydes such as citral adding to its sharp scent. Specifications call for 4.5 to 8.5 percent aldehydes in pressed Mexican-type oil, compared with 0.5 to 2.5 percent in distilled oil. Pressing also carries over non-volatile furocoumarins. Figures in the Cosmetic Ingredient Review (CIR) report put bergapten (5-MOP), the most strongly phototoxic of them, at 0.17 to 0.33 percent of lime oil, far more than in lemon oil. Steam distillation removes these compounds.
In tests reviewed by the CIR Expert Panel, pressed lime oil caused phototoxic reactions in people and in animals, down to 15 percent in hairless mice, while distilled lime oil caused none. The International Fragrance Association (IFRA) therefore limits expressed lime oil to 0.7 percent in products that stay on the skin, and it caps total bergapten from all citrus oils in such products at 15 ppm. EU rules also require furocoumarins to be kept below 1 mg/kg in sunscreens and tanning products. Neither IFRA nor the CIR sets a phototoxicity limit for rinse-off products such as soaps.
The Panel also described an older mouse study in which repeated applications of lime, lemon, orange and grapefruit oils promoted skin tumors started by a chemical carcinogen, and it asked that products be formulated to be non-irritating. For leave-on products, distilled or furocoumarin-free lime oil is the lower-risk choice.
Sources: CIR: Safety Assessment of Citrus-Derived Peel Oils as Used in Cosmetics (2014); IFRA: Standard for lime oil expressed (Amendment 49); IFRA: Standard for citrus oils and other furocoumarin-containing essential oils (Amendment 49)
