Morning routine order
Cleanser, then toner or essence if you use one, then serum, eye cream, moisturizer and sunscreen. The usual rule is thinnest to thickest: watery textures first so they reach the skin, richer creams after them to seal everything in. Sunscreen is always the last skincare step in the morning and goes on before makeup.
Night routine order
Take off sunscreen and makeup first, with a cleansing oil, balm or micellar water, then your usual cleanser if you double cleanse. Follow with toner, your treatment serum or retinoid, eye cream and moisturizer. Night is where strong actives belong, because several of them make skin more sensitive to the sun. A face oil, if you use one, usually goes last.
Serum or moisturizer first?
Serum first. Serums are thinner and are made to deliver concentrated ingredients close to the skin; moisturizer goes on top to hold water in and support the skin barrier. If a product label or your doctor tells you to apply something differently, such as a prescription cream, follow that instead.
Where masks and exfoliants go
Use a mask after cleansing and toner and before serums, two or three evenings a week. Exfoliating acids such as glycolic, lactic or salicylic acid go on clean, dry skin; on those evenings leave out your retinoid. Start any new exfoliant at two or three evenings a week and build up only if your skin stays calm.
Ingredients not to mix in one routine
Retinoids (retinol, retinal, tretinoin) and exfoliating acids on the same evening are the classic recipe for redness and peeling, so alternate the nights. Benzoyl peroxide can break down some retinoids, so keep it to the morning or another day unless a product is made to combine them. Two exfoliants in one routine, or a scrub on top of an acid, is more than most skin can take.
Pairs that are usually fine
Niacinamide with vitamin C, niacinamide with a retinoid, and hyaluronic acid with almost anything work well together for most people. The old warning about niacinamide and vitamin C came from tests with pure ingredients under heat, not from skincare as you use it. If a pair stings, move one to the morning and the other to the night.
How long to wait between layers
Long waits are not needed. Give each layer a minute or so to settle before the next, and give sunscreen a few minutes before makeup. If a prescription product comes with its own waiting time, that one wins.