The cuticle is the thin band of dead tissue that lies on the nail plate just in front of the eponychium, sealing the gap between skin and nail so that bacteria and fungi cannot reach the matrix.
Also known as: nail cuticle, cuticula, true cuticle, cuticle skin
The cuticle is often confused with the fold of skin at the base of the nail. That fold of living skin is the eponychium. The cuticle is the thin, colourless tissue that the eponychium sheds onto the nail plate, where it sticks and forms a seal (Medscape). The seal closes the gap between skin and nail, so bacteria and fungi cannot reach the matrix where the nail is made.
In a manicure the cuticle is pushed, not cut. The advice from Essie is to soften it with a cuticle remover or softener, push it back with a stainless steel pusher, and trim only hangnails, the small tears of skin at the side. Soaking in water is avoided because the nail absorbs water and swells, which later leads to chips (Essie).
Cuticle left on the plate stops polish from bonding. It lifts the film at the base and the manicure grows out with a gap. Pushing the cuticle back and wiping the plate with alcohol or remover before the base coat is part of standard prep.
Daily oil keeps the cuticle and the skin around it supple. Dermatologist Dr Hadley King recommends keeping the skin around the nail moisturised so that pathogens are less likely to get through (Today). Jojoba, sweet almond and vitamin E oils are the common choices. In winter, an occlusive balm over the oil overnight, known as nail slugging, traps the moisture.