NaillyCuticle oil is a blend of skin-conditioning oils (jojoba, almond and vitamin E are classic) applied to the skin around the nail. Its reputation as the single highest-leverage habit in nail care is deserved, and the mechanism is unglamorous: gel and enhancement products live or die at their seal edges, and the skin bordering those edges flexes thousands of times a day. Oiled, flexible skin does not pull at the seal; dry, tight skin does.
Applied morning and night, cuticle oil measurably extends how long a set looks fresh, keeps hangnails away, and improves the health of the new nail growing in. The trick is logistics, not chemistry: keep one bottle at your desk and one by your bed, because the habit only survives if the bottle is within reach.