What actually makes the scalp oily
Oil on the scalp is sebum, made by tiny glands attached to hair follicles. Those glands respond to signals such as hormones and individual biology; shampoo mainly removes sebum that has already reached the skin and hair. Washing does not, by itself, show that the glands have received a reliable “make more oil” signal. The idea that they routinely rebound by overproducing after a wash is not well established.
Greasy hair can still seem to return quickly after washing. Sebum continues to reach the scalp, and its visibility depends on how much accumulates, how it spreads along the hair, and how long it has been since the last wash. Fine or straight hair may show oil sooner because it tends to lie close to the scalp, while curlier or coarser hair can make oil less noticeable along the strands.
Choose a routine by how your scalp feels
Washing frequency is a practical matter, not a test of whether the scalp has been “trained.” Some people prefer daily washing; others are comfortable washing less often. Shampoo cleans the scalp, but a formula that leaves it dry or irritated may be a poor fit, and conditioner is generally used on the lengths rather than rubbed into the scalp.
The useful distinction is between oil returning on its normal schedule and discomfort from the wash itself. Daily shampooing does not automatically cause a greasier scalp, but the right interval and product depend on the person—and on whether the scalp feels clean and comfortable afterward.
