Hair Oil & Serum

Two very different products share this shelf. Plant oils such as argan, jojoba and sunflower sit largely on the surface, though coconut is one of the few small enough to move into the strand itself. Silicone serums, listed as dimethicone or cyclomethicone, do not absorb at all. Instead they leave a clear, slippery film that reflects light and blocks humidity. Read the first three ingredients and you know which one you bought.

Frizz is a humidity problem and the fix is physical. Hair swells as it takes on water from the air, and swollen strands push out of alignment, which is the fuzz you see. A surface film slows that water getting in, so the strand keeps its shape for hours in damp weather. Shine follows the same logic, since light bounces off a smooth surface and scatters off a rough one. Neither effect is repair. Split ends cannot be rejoined, only glued flat until the next wash, so trimming stays the only cure.

A mask goes in and gets rinsed away; oil stays on and never goes in. Water is what a leave in brings and what oil lacks, so one hydrates and the other seals. Putting oil on dry, thirsty hair with no water based product underneath is the common mistake that buys shine and no softness. Styling products deliver hold, which oil never does. Pre wash oiling is a separate technique, where oil goes on an hour before shampoo to cut how much the wash strips out.

Coarse, curly, thick and color treated hair drinks it happily, and humid climates make the case on their own. Two or three drops rubbed between palms and pressed onto the last few inches is the dose for fine hair, and it never belongs near the scalp. Oily roots and fine flat hair should treat this as a weekly ends treatment or leave it alone. Silicone heavy serums also build up over weeks and need a clarifying wash to shift.

Warm the product between your hands first, because oil applied cold lands in patches. Damp hair takes it more evenly than dry hair and needs less of it. A good one shows itself two hours in rather than two minutes in: separated and soft means it is working, stringy means you overdosed. Light spoils plant oils, so keep bottles in a cupboard, and treat a sharp crayon smell as the sign that the bottle is finished.