"Olive, argan, avocado, and coconut oils are rich in fatty acids," says Alexandra Kowcz, vice president of R&D at Beiersdorf, “which help leave your skin softer and smoother.” For hair, the effects are equally brilliant: These oils reduce breakage and increase the hair’s ability to retain moisture, says cosmetic chemist Ni'Kita Wilson. Our picks for which to use when...

1. Olive Oil
What it is: Produced by pressing whole olives, this oil is rich in oleic, linoleic, and palmitic acids, along with polyphenols and vitamin E, antioxidants that help protect the skin from free radical molecules generated by the sun and pollution.

Best for: antiaging

Try: Bobbi Brown Remedies Skin Fortifier No. 93 Strength & Recovery Tonic, $45; BobbiBrownCosmetics.com

2. Argan Oil
What it is: Extracted from the kernels of the fruit of a tree indigenous to Morocco, argan oil contains antioxidant vitamin E, moisturizing squalene, and oleic and linoleic acids.

Best for: soft, shiny hair

Try: Garnier Whole Blends Illuminating Moroccan Argan & Camellia Oil, $6.50; drugstores

3. Avocado Oil
What it is: Pressed from the rich pulp surrounding the fruit’s pit, avocado oil is packed with omega fatty acids and antioxidants vitamins A, C, and E, says Kowcz.

Best for: moisturizing

Try: Nivea Nourishing Body Oil, $12; drugstores

4. Coconut Oil
What it is: Culled from coconut meat, this oil is loaded with antioxidant vitamin E and lauric acid, an anti-inflammatory. Coconut oil can deeply penetrate the hair shaft, so it’s ideal for strengthening coarser hair types, says Wilson. If you have fine strands, avoid coconut oil, as it can weigh hair down.

Best for: hair repair

Try: Kérastase Aura Botanica Essence d’Éclat, $43; Kerastase-USA.com

Shopping Smarts: Look for a leave-on product with oils appearing in the middle to top of the ingredients list. A rinse-off product won’t come in contact with skin or hair long enough to have a noticeable effect.

Photos by Jeffrey Westbrook/Studio D.

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