Limonene is one of the most used fragrance ingredients in skincare products. It is, in fact, one of the most used compounds in skincare products in general. Pure limonene is a clear, volatile liquid (this means that if you leave a bottle of limonene open, it will evaporate quickly and distribute its scent into the air).
Limonene can be naturally found in the peels of citrus fruits and in coniferous trees. It has a fresh, pleasant, citrusy smell. It is not only a commonly used fragrance in skincare products, but also in foods, cleaning solutions, and air fresheners.
It also has some anti-inflammatory properties and has been shown to help wounds heal. It is also, believe it or not, an effective insect repellent. Pure liquid limonene is a remarkably efficient solvent for other water-insoluble substances.
Similar to other essential oils and their constituents, undiluted limonene should never be applied directly onto the skin. Limonene is used only in single-digit percentages or less in skincare products, so there should be nothing to worry about in this matter.
People who are sensitive to citrus fruits and citrus fragrances, however, should still try and avoid products containing limonene. This sensitivity might worsen if limonene or any other citrus essential oil has been left unsealed to oxidize.