Common Misconceptions of Skin Care Terminology

Why is skin care always so confusing?!

Ever since I started reading about skin care, I always see people address serums and moisturizers as if they were distinct and separate types of products; same goes for moisturizers with SPF and sunscreens. Therefore, I’m writing this post to explain why they’re both inaccurate, and how a better understanding of these concepts can be of assistance as you attempt to comprehend and construct the ideal routine.

Moisturizers versus Serums

Incorrect Definitions:

  1. Most people define a moisturizer as any heavier non-silicone-based leave-on product that prevents the skin from becoming dry.
  2. On the other hand, a serum is defined as a lightweight silicone-based leave-on product whose purpose is to deliver high concentrations of beneficial ingredients to the skin.


Glycerin is an occlusive agent, humectant, and emollient. Talk about a triple threat!

Because dry skin or xerosis is characterized by decreased water content in the stratum corneum (SC), the main purpose of a leave-on product is to prevent further loss, which is known as transepidermal water loss (TEWL). Therefore, the main component of a leave-on product is some type of occlusive agent, which will form a superficial barrier that is to an extent, impermeable to water. To further increase the water content of the SC, humectants are often included to bind to excess water, and deliver it into the skin. And since most leave-on products contain a lot of water, there’s plenty to go around. Finally, leave-on products may also contain emollients, whose purpose is to proliferate through and fill in the cracks of the SC, in order to soften and smooth the appearance and texture of the skin.

Okay, we’ve addressed the characteristics necessary to prevent the skin from becoming dry. But do the additions of silicones and other beneficial ingredients differentiate moisturizers from serums? Fortunately, that is easily answered. Silicones are just other types of occlusive agents; think of them as lighter forms of petrolatum. And high concentrations of beneficial ingredients like antioxidants can and should be included in all leave-on products, not just “serums.”

So is there any characteristic that is exclusive to either moisturizers or serums? Nope.

Correct Definitions:

A moisturizer is a leave-on product that contains occlusive agents, and may also contain humectants, emollients, and other beneficial ingredients. A serum is a type of moisturizer that tends to have a lighter texture. But they’re essentially the same thing: a serum can function as a moisturizer for oilier skin types.

Moisturizers with SPF versus Sunscreens

Incorrect Definitions:

I don’t actually know how people (in their minds) differentiate moisturizers with SPF from sunscreens. But I always see people give this distinction, without giving an explanation. For example, a reader recently commented that:

“… HOWEVER, the LRP is actually a MOISTURIZER with SPF rather than a straight sunscreen. So I was wondering if the PCA Sunscreen you recommend is moisturizing as well or would it require an additional moisturizer?…”


The Josie Maran Daily Moisturizer SPF 40 is one of my favorite moisturizers with SPF AND sunscreens to recommend to people with drier skin types.

Now that we’ve defined what a “moisturizer” is, a moisturizer with SPF is therefore just a leave-on product that contains occlusive agents AND UV filters, and may also contain humectants, emollients, and other beneficial ingredients. What about sunscreens? I honestly don’t know what to say, except that sunscreens are the exact same thing. They can certainly be “moisturizing.” In fact, a common complaint is that “sunscreens,” especially those that contain inorganic UV filters like titanium dioxide and/or zinc oxide, are TOO moisturizing, greasy, emollient, and/or heavy. So I don’t understand how this distinction was imagined in the first place. I mean, anything with an SPF rating is measured the same way; a “moisturizer” with an SPF of 20 and a “sunscreen” with an SPF of 20, will both provide the same initial level of UVB protection.

Correct Definitions:

Moisturizers with SPF and sunscreens are the exact same thing: leave- on products that contain occlusive agents AND UV filters, and may also contain humectants, emollients, and other beneficial ingredients.


So how can this newfound knowledge help you? Here’s an example. Another reader recently wrote this comment:

“…I’m a little concerned the Glycolix Facial Cream would prevent the BHA from penetrating, but I’m told applying moisturizer within several minutes of cleansing is key…”

Basically, the reader is hesitant on me asking her to apply a BHA product and then to wait around 30 minutes before applying the Glycolix Facial Cream, because she’s been told that you HAVE to apply moisturizer within several minutes after cleansing.

Now, dermatologists (and others) recommend applying a moisturizer a few minutes after cleansing in order to reduce TEWL. The longer you wait, the more water will be lost to the atmosphere.

But here’s the thing. Because salicylic acid is volatile, it requires some type of carrier that isn’t water (though water is necessary; think pH), in order to inhibit the rate of evaporation. But in doing so, the carrier will also act as an occlusive agent for the skin; thereby reducing TEWL. And if we go back to our revised definition of a moisturizer: “a leave-on product that contains occlusive agents, and may also contain humectants, emollients, and other beneficial ingredients,”  a salicylic acid product would satisfy the requirements necessary for it to be a “moisturizer.” Why? It’s because it contains occlusive agents, which will reduce TEWL. Yes, it may not be a very good moisturizer, but it will do perfectly fine for the 30 minutes or so wait time that I recommended before applying another product.

Yay, a cause for celebration!

See how handy these re-imagined definitions can be?

Anyways, feel free to share your thoughts and any of YOUR newfound insights and/or realizations in the comment section below.

Thanks for reading.

P.S. Thank you everyone for your support in the past week! The last post on the interaction between niacinamide and L-ascorbic acid is now in 1st place for being the most-commented non-giveaway post in the history of FutureDerm! That’s right; it’s first out of 1,272 posts! And we achieved this honor in less than a week! Yes, almost half of those comments were my responses to other people… but whatever. I’ve also never had two of my posts be the 1st and 2nd most popular ones of the week. Nice job everyone!  

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  • @casey

    Please read the response I wrote to @Kristina above. I hope it answers our questions. 🙂

  • @Kristina

    First, I only recommended the Josie Maran SPF 40 for drier skin types, as I indicated in the post. And drier skin types are less prone to acne.

    Second, the list itself is a useful tool to help avoid products that may worsen acne. However, nothing on the list “causes” acne so to speak. They just have varying potentials to exacerbate acne. It’s mostly due to the fact that a lot of them are similar to components of sebum, and since acne can’t exist without sebum, the more there is, the more likely the chances of getting acne. Also, the list is certainly not all-inclusive.

    So my recommendation is to use lists like these to help weed out products that may not be appropriate for your skin type. However, I wouldn’t use this list to justify not using a product just because it contains one of these ingredients. You have to consider all the ingredients as a whole product. Weigh the pros against the cons. For example, one of the best retinol products on the market contains a tad bit of these ingredients. However, its use have absolutely provided a ton of benefits for my skin. And I almost never breakout these days. It’s all about finding the right balance for your skin. But I reiterate, don’t be too hasty and disregard a product just because it contains one or more of these ingredients.

    Does that make sense? I’ll definitely be writing a post on this topic in the future, because I’ve seen it mentioned so many times.

    Thanks for reading!

  • casey

    small world kristina, i went to face reality too! lol. i stopped going there because it was getting too expensive but they did great things with my acne.

    i think the head esthetician you’re referring to is laura…she’s great. i can also vouch that she studied under dr. fulton.

    and i go off the pore clogging list too! would also love to get your feedback on this john.

  • Kristina

    I used to be a client of a fairly well-known acne clinic in the San Francisco Bay Area called Face Reality. According to their pore-clogging ingredients list, Josie Maran Daily Moisturizer SPF 40 has pore-clogging ingredients and is not good for acne-prone skin. It has Ethylhexyl Palmitate and Isopropyl Palmitate.

    I believe this list goes off of Dr. James Fulton’s (co-developer of Retin-A) research on acne. When I used to be a client, the head esthetician worked and studied under Dr. Fulton and I would talk to a lot of other clients in the waiting room who used Retin-A and had acne issues, due to the reformulated Retin-A (with pore-clogging ingredients isopropyl myristate) after Dr. Fulton sold it.

    I’d love to get your feedback on this John. Is there any merit to it? I’ve been using this list for all my skin care products and unfortunately, because of this list, I have to skip over many recommended products here on FutureDerm and from your blog because they contain pore-clogging ingredients!

  • @janine

    You’re welcome! The only reason why I keep mentioning the Josie Maran SPF 40 is because I forgot to include it in the sunscreen recommendations post that everyone can see. I’m debating whether or not it would be helpful to simply edit that post to include the Josie Maran…

    But yeah, I really like the product because its lotion-like texture is elegantly rich; it provides excellent UVA and UVB protection, doesn’t leave a white-cast, and is reasonably priced. It’s great for drier skin types!

    I hope that make sense and thanks for commenting!

  • @Soi Dog

    Okay, I know you’re worrying about all this whole layering issue. The first thing you need to do is relax. Take a nice, deep breath. While skin care is very important (clearly, considering my career choice) topical skin care can only do so much. So slight variations in how “effective” your skin care routine is, isn’t going to make to make a significant difference when you consider everything that affects your skin’s overall health.

    Now, most skin care products are some type of emulsion based on water and something else, whether it’s a lipid, silicone, or petrolatum-based compound. So when you apply an oil-in-water emulsion, water is the continuous phase, which means that it’s the primary solvent. Therefore, when the first OiW emulsion sets, that means that the water content has evaporated. As long as the product you’re applying afterwards also contains a lot of water, the water from the 2nd product will rehydrate the first “set” layer and allow the second prouct to penetrate. Some occlusion may occur, but it’s much more practical than to apply, cleanse, apply, cleanse, etc… Yes, you may deliver slightly more ingredients to the skin if you do that, but you’re going to damage the skin more with the constant cleansing. It would be an overall net loss in helping your skin.

    Ultimately, the decision is yours. But in my opinion, as long as the two products you’re applying are similar to each other, the ingredients in both will penetrate adequately. I’d rather have you do that than wash and reapply 4x a day.

    Also, to work around this obvious source of stress for you, try to find multi-purpose products. Or if you’re comfortable and knowledgeable with the products and their compatibility, mix the two together.

    I hope that helps, and remember, breathe! Great name by the way!

    P.S. I’ve put this topic down in my to-do list. So stay tuned!

  • @berk

    Yes, products that are emollient tend to take longer to set on the skin. But from a glance, both products that you mention doesn’t appear to be overly thick and emollient. Waiting around 5 minutes before putting on your clothes should be fine.

  • On behalf of those of us who are constantly in search of perfecting our skin care regimen, I want to thank you for yet another enlightening post!
    This is the third time you have mentioned the Josie Maran Daily Moisturizer SPF 40 and I wondering what it is specifically that has you so exicited about it?

  • Soi Dog

    Hi John,

    Thanks for clarifying the points above.

    I find myself stuck inside the question surrounding absorption of layered products when you’ve made it clear that serums, moisturizers, with and without SPF, contain occlusives and/or humectants and/or emollients.
    After the first layering of a skincare routine, designed to deliver vitamins (as an example), would subsequent layering of say an antioxidant product not be somewhat limited in it’s absorption by the effect of whatever occlusives/humectants/emollients are in the first formulation applied?
    I stick to very light serums and creams with lots of beneficial ‘active’ ingredients but always feel unsure about the second layering as my skin is always a little tacky to the touch and uncertainty remains as to whether my skin actually absorbes a product applied second, through the moisture barriers created by the first.

    I am not referring to sunscreen here, I am nocturnal and use separate and excellent protection even inside when around in the light, from which I have no other expectation.

    John, is it reasonable to expect my layered products are reaching their target areas in the skin or are some being ‘occluded’ by previous application of others – I don’t like to waste money and will apply separately after cleansing again at a later time if there is more benefit to be had this way – I have the time, so could do it this way if you think it’s better but it would mean cleansing 4+ times/day???

    Thank you for your consideration, I hope someone else can benefit from your answer to this question, I’m sure others must have pondered it also unless their skin soaks up everything instantly.

  • berk

    Thanks for the reply John! Yes, that does make sense. But can you clarify– if a product is more emollient, does that mean it takes longer to “set?”

    FYI– the hydroquinone I use is 4% hydroquinone Obagi Clear. Do you think it needs a long time to set?

    I also sometimes use Glytone 17.5% glycolic acid Body Lotion

  • @berk

    It just depends on how long it takes for the HQ product to “set” or because basically transfer-resistant. That number can vary widely depending on how emollient the vehicle or carrier is. It really just depends on each individual formulation. But as long as the product sets and you aren’t rubbing that area, the HQ will penetrate into your skin just fine.

    Also keep in mind that any time you see a time estimate, whether it’s 10 minutes (in your case), or 20, 30… remember that those are just guesses. Don’t feel like if you only wait 9 minutes, the product isn’t going to work at all.

    Does that make sense?

  • @casey

    Thank you! I have so many things planned for my blog; it’s just so busy and stressful to even think about doing the massive amount of work ahead of me. Lol! But I will keep doing my best.

  • berk

    Perhaps you can clear up this misconception too:

    Is it true that one has to wait at least 10 min after applying any active ingredients or even lotions on the body before dressing due to possible transfer from skin to clothes? I see it written all over beauty and skincare forums.

    In my case, I just started applying hydroquinone on some of the acne pigementation on my legs and arms. Do I have to wait at least 10 minutes before getting dressed? I definitely wouldn’t want the hydroquinone to transfer from my skin and onto my clothes. I want it to stay on my skin!

  • @Martine

    Well, to answer your question, just because something is too matte and/or drying for you, doesn’t mean that it’s too drying for someone else. For example, no matter why sunscreen I use, I still get oily throughout the day. Therefore, it’s still a “moisturizer” for me. Do you understand what I’m saying? You can’t say a sunscreen isn’t a “moisturizer” with SPF for every person out there, because you can’t know everyone’s skin type. Conversely, there are lots of things labeled as “sunscreens” that are way too emollient for many people. But it’s still a moisturizer with SPF; they’re all still moisturizers with SPF. It’s just not the right one for my skin type.

    Does that make sense?

    Thanks for commenting!

  • @Erika

    I appreciate your continued enthusiasm. I always recommend applying a separate antioxidant product before your sunscreen, so it’s great that you apply something beforehand anyways.

  • casey

    looking forward to more posts by you and also your updated skin routine on your own blog. keep up the good work!

  • Martine

    Hi John- great advice 🙂 thank you. I work in retail skin care sales and these questions are frequently asked. My only question is (and maybe I am over thinking) is the SPF vs facial moisturizer with SPF. I agree with your explanations just have a hard time with that they are one in the same. For instance, if I were to stop by my drugstore and pick up neutrogena spf 30 sunscreen and apply that every day, how would that help my dry skin? The texture of a water resistant sunscreen is completely different from a face lotion with SPF. Yes, they have some antiox and a good texture but its not enough. Most sunscreen typically water-resistant, oil free or sport with higher spf these usually dry to a matte finish and not run into someone eyes when they are active. If someone just applies regular face lotion with an SPF and goes for a jog. So does the lotion. Right in there eyes! Ouch!! 😉

  • Erika

    Excellent read once again John!! 🙂 Gosh I love your posts!

    I particularly liked the section about moisturizers w/ SPF and sunscreens. My experience has been with zinc oxide-based sunscreens. I usually use sunscreens with 15-17% zinc oxide (I’m outdoors almost all the time) and I find the high percentage of zinc oxide is drying, which is why I apply moisturizer beforehand.

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