With hair treatments, you usually have to choose between aesthetic or function: A serum smooths; a leave-in conditioner treats. But hair oils can multitask, serving as a styler that tames frizz and boosts shine and as a repairing treatment — all at once. With summer here in its full glory, there’s no product more perfect than that. A good oil can be that effortless leave-in you need for gorgeous hair, whether you are hitting the beach, going to brunch, or bopping around running errands. Many are packed with highly concentrated botanical oils and rejuvenating ingredients, where a teensy drop makes air drying or styling easy breezy. From strengthening formulas that repair damaged strands to featherweight oils that make hair glossy and free of humidity frizzies, the hair oil you need all season long is right here.