Tawni Bannister for Byrdie
Quick: What's the difference between a serum and a moisturizer? If you're a little stumped about the age-old serum vs. moisturizer question, don't worry! First, this is not a pop quiz, and second, we've called in the pros to help us sort this out. Herewith, read all about serum vs. moisturizer: From how the skincare products are different, to what each of them does, and how they can be used together to amp up skin health. Keep reading to finally uncover how serums and moisturizers differ—and to get pro tips on incorporating both into your skincare regime.
Meet the Expert
- Corey L. Hartman, MD, FAAD, is a board-certified dermatologist and the founder of Skin Wellness Dermatology in Birmingham, Alabama.
- Deanne Mraz Robinson, MD, FAAD, is a board-certified dermatologist based in Westport, Connecticut.
- Noelani González, MD, FAAD, is a board-certified dermatologist based in Bayamón, Puerto Rico.
- Dr. Tiina Meder is a dermatologist based in London and the founder of Meder Beauty.
What Is Serum?
"Serums are typically lightweight formulations that deliver potent concentrations of actives," explains dermatologist Corey L. Hartman. "They are usually thin and absorbent, leaving little, if anything, remaining on the surface of the skin."
Serums can take different forms. "Traditionally, the name serum was used to describe water-based skincare products," explains London-based dermatologist Dr. Tiina Meder. "Sometimes, you can see oil-based serums, but it is not common." Meder explains that serums can used for daily skincare, or as part of an active regime that targets specific needs such as acne, dryness, or age-related changes to the skin. Common types of serums include hyaluronic acid and vitamin c.
What Is Moisturizer?
"Moisturizers use a thicker formula to create a physical barrier that locks in hydration and prevents skin from drying out," says dermatologist Deann Mraz Robinson. "Additionally, they can enhance the functioning of the stratum corneum (the uppermost layer of skin that's made up of fat and oil skin cells) to help retain moisture." The key functionality of moisturizers is, naturally, to moisturize the skin, and thus they typically contain ingredients like the following:
- Hyaluronic acid
- Ceramides
- Organic oils such as macadamia, sweet almond, meadowfoam, borago, and enotera
- Vitamin E
- Carrageenan
Some moisturizers have added anti-aging ingredients, so they do double duty for your skin. But to address a difficult skincare problem (think: sun damage), you may want to combine your moisturizer with a quality serum.
Serum vs. Moisturizer
Serums are thinner in consistency and are intended to deliver potent active ingredients like vitamin C or hyaluronic acid, while moisturizers deliver moisture to the skin and support the skin barrier. "Serums are intended to penetrate deeply into the skin to deliver targeted active ingredients, whereas moisturizers help to fortify the surface of the skin, bind skin cells together more effectively, and work at the surface of the skin to increase hydration," says Hartman.
Moisturizers also may have larger molecules than serums. This means that a moisturizer usually won't penetrate the skin as deeply, or as quickly, as a serum will. This can be a double-edged sword: If you're looking for strong effects, you should be relying on your serum, but if you're looking for continuous hydration, that's your moisturizer's job.
Byrdie Tip
If your skin is oily, a serum may give you enough hydration and eliminate the need for a moisturizer.
Can You Use Serums and Moisturizers Together?
Dermatologist Noelani González says that layering a serum and a moisturizer "can be very helpful for those with very dry skin." She explains: "The serum will help deliver any active ingredients, and the moisturizer will help lock in moisture in the skin, seal in the serum, and help potentiate its active ingredients." That said, if you have acne-prone skin, it may be best to avoid an oil-based serum.
How to Layer Serums and Moisturizers
When it comes to layering skincare products, order matters. "In general, skincare products are layered from thinnest to thickest with the thinnest products being applied to the skin first. If you think about the intended goals, it makes sense. Serums are intended to deliver active ingredients deep into the skin and the moisturizer forms a seal to make the serums more efficacious," explains Hartman.
To effectively layer your serum and moisturizer, first rub the serum onto your face and neck. Then, wait 30 to 60 seconds before applying your moisturizer on top. "The reason for waiting is that you want the serum to settle in before you apply the moisturizer," notes González.
When to Apply Serum
While most serums and moisturizers are used both in the morning and evening, there are some serums or creams that should only be used at night depending on their ingredients.
According to Dr. Meder, any skincare based on active forms of retinol, including retinol itself, retinaldehyde, and retinoic acid, should only be used at night. "Retinol can be quickly excited by ultraviolet rays and transformed into harmful and less efficient substances," she explains.
Be sure to read the instructions on the products you are using to find out which you should use in the morning and which you should use at night. And as always, consult with your dermatologist if you're in any way unsure."
The Final Takeaway
If you have an issue with your skin that you'd like to improve, such as dark spots or early signs of aging, adding a targeted serum product to your daily skincare routine can help improve the appearance of your skin. And for those with dry skin, the right serum and moisturizer combo really may make all the difference.
