In a skin care routine, it is often better to apply serum before moisturizer. This is because serum is typically more lightweight, whereas moisturizer tends to be thicker.

Applying serum first can also give the skin more opportunity to absorb the active ingredients. In many skin care routines, moisturizer is the last step.

Below, we cover everything a person needs to know about choosing a serum and moisturizer, including what they do, the types available, when to apply them, and combinations of ingredients to avoid.

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Often, it is better to apply serum before moisturizer. This is true for several reasons.

The first is that many serums are thin fluids or gels with water-based formulas. This means that they contain no oil and are lightweight products.

By contrast, many moisturizers contain oil and are thicker than serums.

Because oil repels water, applying an oil-based moisturizer before a water-based serum might keep the skin from absorbing the ingredients in the serum.

Another reason is that serums typically have smaller molecular structures than moisturizers. This allows them to deliver ingredients deeper into the skin. A serum might aim to:

  • reduce the visible signs of aging
  • reduce sun damage
  • treat acne or blocked pores
  • ease redness or irritation
  • soothe dry, flaky skin
  • reduce hyperpigmentation

Applying serum first allows the active ingredients to have maximum contact with the skin, before other products.

It can be difficult to decide when to apply different skin care products for maximum effectiveness. Fortunately, the right order tends to be similar, regardless of a person’s skin type or the products they use.

For example, a basic routine for the morning might include:

  • a gentle cleanser
  • moisturizer
  • sunscreen

A basic routine for the evening might include cleanser or makeup remover, followed by moisturizer.

Some people use facial oils. These can be an alternative to moisturizers, as they also seal in moisture. Because they can leave a shiny finish, facial oils may be better suited for use before bed.

People who want to add a serum to their routine can apply it after cleansing and before moisturizing. This could be in the morning or evening, depending on the product.

The best serum depends on a person’s goals for their skin care. Before making a choice, it is important to research a product’s active ingredients.

Skin care products contain inactive and active ingredients. Inactive ingredients help give the formula its consistency or texture. Active ingredients help it achieve an aim, such as treating acne.

Both serums and moisturizers can contain active ingredients, and some do not mix well. This can lead to interactions and side effects. Or, the products may just be less effective together.

To avoid these issues, dermatologists generally do not recommend using too many active ingredients at once. Instead, focus on one or two key ingredients. Introduce them one at a time, if possible, to check how well the skin tolerates them.

Below, learn about some active ingredients in serums and what they do:

IngredientActionSide effects
vitamin A and retinoidspromote collagen production
minimize fine lines
reduce pore size
treat acne
reduce scarring
even skin tone and texture
increased sensitivity to UV light
peeling or flaking
vitamin Cmay brighten the skin
reduces hyperpigmentation
niacinamidereduces inflammation
minimizes pores
reduces oil production
reduces water loss from the skin
alpha hydroxy acid (AHA)removes dead skin cells
increases cell turnover
may reduce hyperpigmentation
increased sensitivity to UV light
mild tingling or burning
beta hydroxy acid (BHA)removes dead skin cells
unblocks pores
treats acne
reduces oil production
increased sensitivity to UV light
mild tingling or burning
hyaluronic acidattracts moisture
plumps the skin, reducing fine lines
aids in skin healing
rarely, contact dermatitis
peptidesencourage the production of collagen and elastin
reduce the signs of aging

For anyone using retinoids, AHAs, or BHAs — even just periodically — it is important to wear sunscreen every day. Choose a water-resistant, broad-spectrum sunscreen with an SPF of 30 or above.

Some active ingredients are unsuitable for certain people. For example, people who have rosacea, hormonal acne, or severe scarring should speak with a dermatologist before trying an over-the-counter product with retinoids. People who are pregnant or nursing should not use these products.

If in doubt, consult a healthcare professional.

Some serums and moisturizers have ingredients that are better suited to morning or evening use only. These include products containing:

  • Vitamin C: Since many people use this product to brighten their skin, it may be more desirable to use it in the morning.
  • Retinoids: These increase the skin’s sensitivity to the sun, and they can cause some irritation. For this reason, it is better to use retinoid products before bed. If the product is a serum, using a soothing moisturizer afterward may prevent or ease any side effects.
  • Exfoliants: These products can also increase sensitivity to the light, so a person may prefer to apply them before bed. This may also mean that the product remains longer on the skin.

Combining certain skin care ingredients, even in different products, may irritate the skin. People should avoid the following combinations:

Retinoids and exfoliants

Retinoids can be intense treatments and can cause side effects. Having acid exfoliants at the same time may be too much for some peoples’ skin.

Also, both substances increase sun sensitivity, so combining the two may make the skin especially susceptible to damage. Instead of using both products every day, try using them on different days or alternating for longer periods.

Retinoids and benzoyl peroxide

Layering retinoids and benzoyl peroxide may cause excessive dryness and irritation. Some believe that retinoids deactivate benzoyl peroxide, but a 2010 laboratory study did not find this.

The scientists combined 0.05% tretinoin gel and a 5% benzoyl peroxide formulation. After 7 hours, 100% of the tretinoin was still active.

In general, it is best to apply serum before moisturizer. This gives the active ingredients in the serum the best chance of working. Otherwise, the best order and time of day for a skin care routine depends on the products’ ingredients and the person’s goals.

A dermatologist can describe the best approach based on a person’s concerns and needs. Also, contact a dermatologist about any persistent skin issues, such as dryness, acne, scarring, or hyperpigmentation.