Carrier Oils in Soap: Matching Oils to Your Skin Type
- The Humble Shepherd
- 2 days ago
- 13 min read
When people fall in love with handmade soap, they often start with the obvious details: scent, colour, swirl.
Behind every bar though, there’s a quieter decision that makes a huge difference to how your skin feels after you step out of the shower: the carrier oils.
In cold process soap, carrier oils are the main plant oils and butters that react with lye to form soap. The mix you choose affects everything from lather style to how soft your skin feels afterwards. Over time, studies have shown that different plant oils can either support the skin barrier or, if used in the wrong way, make dryness and irritation worse. A landmark dermatology review on topical plant oils and skin health highlights just how differently olive, sunflower, coconut and other oils behave on human skin.
In this guide, I’ll walk you through how carrier oils work in soap, what the research says about natural oils and the skin barrier, and how to choose bars that make sense for your own skin type rather than guessing at random.
What Are Carrier Oils in Soap?
In soapmaking, carrier oils are the main vegetable oils and butters: olive, sunflower, coconut, shea, cocoa butter, and so on. During saponification they react with sodium hydroxide to become soap and glycerin.
A few key points:
Different oils create very different soap molecules and by-products.
Some oils make a bar very cleansing, some make it extra conditioning, some help hardness and longevity.
A portion of the oils is often left unsaponified (this is called “superfat”), which means a small amount of whole oil remains to cushion the skin.
Dermatology reviews on natural oils underline that composition really matters. Oils richer in linoleic acid tend to support barrier repair and hydration, whereas oils very high in oleic acid can sometimes weaken the barrier if used in the wrong way or under occlusion.
So when I choose carrier oils for a bar, I’m not just thinking “What smells nice?” I’m asking:
What kind of skin is this bar for?
How much cleansing is appropriate?
What mix of fatty acids will feel comfortable for that skin type in a rinse-off product?
What Science Says About Natural Oils and the Skin Barrier
Several large reviews have pulled together what we know about plant oils on skin:
A review in the International Journal of Molecular Sciences looked at a wide range of plant oils and concluded that the linoleic-to-oleic acid ratio is a key factor in whether an oil supports barrier repair or potentially disrupts it when used neat on skin.
A more recent paper in ACS Omega on plant-based cosmetic oils confirmed that oils such as sunflower, olive, argan and jojoba contain vital fatty acids and emollients that hydrate and soften skin, but also stressed the importance of formulation and context (leave-on versus rinse-off, pure oil versus blend).
A 2024 review on the benefits and challenges of natural oil treatments cautioned that while natural oils can be beautiful barrier-supporting moisturisers, they can also clog pores or irritate sensitive skin if chosen poorly.
For soap specifically, another review on skin cleansing with soaps versus synthetic detergents explains that classic soap is naturally more alkaline, so the gentleness of a bar depends heavily on the recipe and superfat, not just the fact it’s “handmade”.
That’s why at The Humble Shepherd, I’m always thinking in layers:
Which oils and butters support barrier comfort?
How much cleansing power is truly needed?
How can I balance the fatty acids so the bar works with, not against, your skin?
Quick Soapmaker’s Guide to Common Carrier Oils
Let’s briefly look at how some favourite carrier oils behave in soap and on skin. This is from a soapmaker’s perspective, informed by dermatology and cosmetic science.
Olive Oil
Rich in oleic acid.
Creates a gentle, conditioning bar with a more lotion-like, low-bubble lather.
Tends to suit normal to dry skin in rinse-off products, especially when blended with other oils.
Reviews of natural oils note that olive oil can be softening but, when used neat and under occlusion, it may irritate some people’s skin barrier. There are even rare reports of contact dermatitis caused by olive oil, particularly in occupational settings where hands are exposed constantly.
In soap, where olive oil is rinsed off and used in a blend, it’s usually far more forgiving.
Sunflower and Rice Bran Oil
Higher in linoleic acid than olive oil.
Help support the barrier and are often recommended in dermatology literature for dry or atopic skin in moisturisers.
In soap, they soften the feel of the bar and the post-wash feel of the skin.
A cosmetic science blog for formulators, the NYSCC overview on natural oils, highlights sunflower and similar oils as workhorses for dry skin because they help replenish essential fatty acids.
Coconut Oil
Very cleansing, high in lauric and myristic acids.
Brings big, fluffy lather and hardness to the bar.
Can feel drying if used at very high percentages without enough balancing oils or superfat.
Used thoughtfully, coconut oil is a gift for hand soap and gym bars. In a “pampering” facial or body bar though, I usually keep it on the moderate side and rely on other oils to bring comfort.
Shea Butter
Naturally rich in stearic and oleic acids, with unique unsaponifiables that many people find soothing.
A key ingredient discussed in both plant oil skin-barrier reviews and cosmetic oils overviews, often recommended for dry, atopic or aged skin.
In soap, shea adds creaminess, richness and a softer after-feel.
Castor Oil
Very high in ricinoleic acid.
In leave-on products, it is known as a heavy but deeply conditioning oil, often recommended to soften rough patches and cuticles – magazines like Good Housekeeping regularly highlight its ability to bring shine and moisture to dry skin and hair.
In soap, I use it sparingly (often 3–8 percent) to boost and stabilise lather.
Jojoba, Avocado and “Special” Oils
Jojoba is technically a liquid wax, with a composition quite similar to our skin’s sebum.
Avocado oil brings vitamins and a plush feel.
A 2024 review of plant-based cosmetic oils lists these among emollients that can support softness and barrier function when formulated well.
In soap I treat these as “accent” oils. They add nuance and marketing appeal, but the core work still comes from simpler, well-understood oils like olive, sunflower and shea.
How Fatty Acids Relate to Skin Types
Many formulators think less in terms of “olive vs sunflower” and more in terms of fatty acid profiles.
Dermatology and cosmetic science papers repeatedly note:
Oils high in linoleic acid (like sunflower and many seed oils) tend to help support impaired barriers and may suit oily, acne-prone or inflamed skin better.
Oils higher in oleic acid (like olive and avocado) feel richer, take longer to absorb, and are often loved by dry or mature skin in leave-on form.
Simple guides for consumers, such as this explanation of linoleic versus oleic acid in facial oils, say the same thing in plainer language: linoleic suits oily or acne-prone skin, while oleic is kinder to dry, fragile skin.
Now, remember we’re talking about soap, which is washed off. Fatty acid profiles won’t act like a leave-on serum. Even so, they still shape how the lather feels, how aggressively a bar cleanses and how your skin feels afterwards. That’s enough to make them worth matching to your skin type.
Carrier Oils for Dry or Dehydrated Skin
If your skin feels tight, rough, or flaky after washing, you're likely dealing with dryness or a weakened barrier. Research consistently shows that emollient plant oils can support barrier repair and hydration when chosen carefully. A review on topical plant oils and skin barrier repair points out that oils rich in linoleic acid, such as sunflower and safflower, tend to be especially helpful for barrier function.
Helpful oils in soap for dry skin
In my own recipes for dry or mature skin, I often lean on:
Olive oil (in moderation) – Very conditioning and traditional in soapmaking. However, several studies suggest that pure olive oil used repeatedly on compromised or infant skin can worsen barrier function, particularly in atopic or neonatal skin. One adult study found that olive oil alone impaired stratum corneum integrity, whereas sunflower seed oil preserved and improved hydration. You can read that comparison in a controlled trial on olive vs sunflower oil and the adult skin barrier.
Sunflower seed oil – A lovely choice for dry skin soaps, with a higher linoleic acid content that supports barrier repair. A systematic review of neonatal skincare found that sunflower oil improved barrier function and skin condition when used appropriately. The findings are summarised in a review on topical oils and neonatal skin barrier.
Sweet almond oil – Often tolerated well by dry skin and frequently used in clinical studies as a moisturiser. A multi-centre trial on xerosis reported that almond, jojoba and coconut oils significantly increased hydration over two weeks, performing comparably to petrolatum; those results are detailed in a study of natural oils on dry skin and barrier properties.
Shea butter and other butters – Rich in stearic and oleic acids, shea creates a creamier lather and a cushioned feel. The same Frontiers review on butters and oils notes that shea and similar butters can support hydration when used as leave-on products, and in soap they contribute to a less stripping wash.
Reviews on natural oils and barrier repair suggest that sunflower and shea can be particularly helpful for dry, rough skin in moisturisers. In a rinse-off bar, they help keep skin feeling softer after washing.
In bars I design for dry skin, I also keep the superfat a little higher and combine these oils with gentle botanicals like colloidal oatmeal. If you'd like a feel for how this translates into finished products, my article on the benefits of choosing handmade soap explains how traditional cold-process bars naturally retain moisturising glycerin and richer oils.
Carrier Oils for Oily or Acne-Prone Skin
Oily and acne-prone skin can be understandably nervous about oils in any form. The reality is more nuanced: some oils are more likely to clog pores than others, and fatty acid balance matters here too.
Dermatology reviews on natural oils and acne note that oils rich in linoleic acid may be better tolerated by acne-prone skin in leave-on products, whereas heavy, occlusive oils can clog pores when overused.
For acne-prone faces and backs, I tend to favour:
High-linoleic oils such as sunflower, safflower, grapeseed, or hemp seed oil, which are often lighter and less occlusive. A recent review on the role of linoleic acid in skin health notes that linoleic-rich oils can help support barrier repair and are frequently discussed in the context of acne and atopic dermatitis.
Jojoba oil – Technically a liquid wax rather than a true triglyceride, jojoba behaves in a uniquely skin-friendly way. An updated review on jojoba oil in cosmetic science reports improvements in hydration and reduced transepidermal water loss, making it a useful component in formulas for combination and blemish-prone skin.
Avoiding heavy, highly comedogenic oils in facial soaps – While the rabbit ear model has limitations, a classic paper on comedogenicity of common cosmetic ingredients catalogues ingredients that frequently lead to comedone formation and suggests using them cautiously on acne-prone skin.
In my own acne-friendly bars, you'll often see a balanced combination of coconut (for cleansing and lather) with a generous proportion of high-linoleic oils and clays to keep the bar effective but not suffocating. If you're curious about how clays fit into that picture, my deep-dive on bentonite clay soap for deep pore cleansing explores that side of formulation.
Carrier Oils for Sensitive or Eczema-Prone Skin
Sensitive skin has less room for error. When the barrier is impaired, oils that are usually harmless can suddenly become irritating. A paper reviewing natural oils for skin-barrier repair emphasises that linoleic-rich oils like sunflower seed oil are generally better tolerated on compromised skin than oleic-heavy oils like olive.
Two particularly important findings stand out for me when formulating for sensitive or eczema-prone customers:
In adults, repeated application of olive oil alone was shown to damage barrier integrity and cause mild erythema, whereas sunflower seed oil did not and instead improved hydration. You can see the details in the study comparing olive and sunflower oil on adult skin.
In a neonatal trial, regular application of olive and sunflower oil was associated with delayed development of the skin barrier, raising concerns about routine use of these oils on newborns. The findings are discussed in a trial of olive oil, sunflower oil, or no oil for baby dry skin.
This doesn't mean these oils must be avoided forever; rather, it highlights why formulation context matters. In wash-off products like soap, they're present as part of a balanced recipe, rinsed away after a short contact time. Even so, for facial bars or ultra-delicate skin, I often:
Rely mostly on olive, sunflower and shea, with very simple formulas.
Try to ensure that bars are unscented or very lightly scented, since essential oils can be surprisingly irritating. A recent paper on essential oils in dermatology lists contact dermatitis and photoallergic reactions among the possible side effects, especially with oxidised oils.
Use colourants sparingly, or not at all.
If you have very reactive or medically complex skin, it's always wise to cross-check your routine with NHS guidance on managing atopic eczema and emollient use, such as the advice on treating atopic eczema with gentle cleansers and moisturisers. Additionally, if you know you have allergies (for example, to nuts or olive), always check ingredients lists carefully. Health resources like Healthline’s guide to olive oil allergy show that while these reactions are rare, they do happen.
Carrier Oils for Combination or "Normal" Skin
If your skin is neither very dry nor very oily, perhaps a little shiny in the T-zone with comfortable cheeks, you likely have combination or what we loosely call "normal" skin.
For these customers, I find that a balanced blend works best:
A cleansing oil like coconut to remove daily build-up
Conditioning oils like olive, sunflower or rice bran
A small amount of luxury oil (jojoba, rosehip, or argan) left as part of the superfat
For a truly combination skin, you can try a two-bar strategy, using a rich, olive and shea-heavy bar for dry areas and the body and a slightly more cleansing bar with a little more coconut or charcoal for the T-zone, shoulders and back. Cosmetic blogs that explain choosing the right facial oil blend often recommend a similar approach with leave-on products: tailor your oils to different zones rather than chasing a single “perfect” product.
Recent work on the biological activity of vegetable oils shows that many common oils mildly promote fibroblast and keratinocyte proliferation, which supports everyday skin renewal, while a few (like certain pomegranate-rich oils) can slow cell growth in vitro. That nuance is discussed in a new study on how vegetable oils influence human skin cells in vitro.
For day-to-day family use, I tend to steer people towards gentle, middle-of-the-road bars rather than highly specialised formulas. If you'd like help simplifying your overall skincare, my guide to building a simple daily skincare routine with natural products walks through a calm, pared-back approach.
How to “Read” a Soap Label for Carrier Oils
Handmade soap labels can look confusing, especially when ingredients are listed in their Latin names or “soap form” (for example, sodium olivate instead of olive oil). A few quick tips:
Ingredients are usually listed in descending order by weight. If you see “Olea europaea (olive) oil” or “Sodium olivate” first, olive oil is likely the main carrier oil.
Look for at least one soft oil (olive, sunflower, rice bran) near the top of the list if you have dry or sensitive skin.
Look for shea or cocoa butter if you want a slightly richer bar.
If you have oily or acne-prone skin, check that there is some cleansing component (such as coconut) but not so much that it dominates the recipe.
Trade groups and cosmetic science bodies often encourage formulators to communicate more clearly about oils. The New York Society of Cosmetic Chemists stresses that consumer understanding of oils is growing, and that transparency builds trust.
At The Humble Shepherd, I’m a big believer in telling you plainly which oils I’ve used and why.
How I Use Carrier Oils in The Humble Shepherd Bars
Behind the scenes, I treat every recipe as a conversation between chemistry, evidence, and lived experience.
For dry skin bars, I dial up shea butter, almond oil and sunflower oil, keep the cleansing factor gentle, and often include oatmeal or honey for extra comfort.
For oily or congested skin, I combine high-linoleic oils with clays like bentonite or French green clay, as I describe in my piece on French green clay soap for oily skin.
For sensitive skin, I keep formulas pared back and fragrance-light, focusing on simple, well-researched ingredients.
Because our products are currently in preparation, you can sign up to the Shop Now waiting list to be notified as soon as these tailored bars are available. Just pop your email into the form and you'll be the first to hear when a new batch is ready.
How to Choose the Right Bar for Your Skin Type
If you're standing in front of a shelf of handmade soaps (or scrolling through an online collection) wondering where to start, here's a simple framework:
Name your main skin concern. Is it dryness, oiliness, sensitivity, or simply wanting to feel a bit more pampered?
Scan the first 3–4 oils on the list Dry skin: look for shea butter, cocoa butter, almond oil, sunflower. Oily/acne-prone: look for sunflower, hemp, rice bran, and clays. Sensitive: look for short ingredient lists, colloidal oatmeal, and simple oils.
Check fragrance and additives. If you're reactive, choose lightly scented or unscented bars and avoid lots of botanicals and colourants.
Treat face and body differently. Even if your body tolerates a richer bar, your face may prefer a lighter, more linoleic-leaning formula. Our article on natural soap for sensitive skin includes tips for face vs body cleansing.
Dry skin: look for shea butter, cocoa butter, almond oil, sunflower.
Oily/acne-prone: look for sunflower, hemp, rice bran, and clays.
Sensitive: look for short ingredient lists, colloidal oatmeal, and simple oils.
Over time, you'll learn which oil blends your skin loves most. The key is to treat carrier oils as tools, not magic bullets.
FAQs: Carrier Oils and Skin Types in Soap
1. Can handmade soap really change my skin, or is it just about feeling nicer?
Handmade soap won't cure underlying medical conditions, but it can reduce everyday dryness and irritation by avoiding harsh detergents and including more skin-supportive oils. Reviews on plant-based cosmetic oils show that many carrier oils have measurable effects on hydration and barrier function when used correctly.
If you're currently using very stripping body washes, switching to a well-formulated bar can absolutely make your skin feel calmer and more comfortable.
2. Are "non-comedogenic" oils guaranteed not to cause breakouts?
Sadly not. Comedogenic ratings are guidelines, based largely on animal models and small human studies. A recent overview of comedogenicity in cosmetic products explains that ratings are best seen as risk indicators rather than absolutes.
Your own skin, overall routine, and genetics all play a part. If you're acne-prone, focus on lighter, high-linoleic oils, avoid leave-on products with known comedogenic ingredients, and patch test new facial bars.
3. Should I avoid olive oil in soap altogether if I have eczema?
Not necessarily. The concerns about olive oil mainly relate to leave-on use on compromised skin, especially on babies or people with active eczema. Studies like the trial comparing olive and sunflower oil on baby skin suggest caution with repeated pure application.
In a wash-off context, where olive oil is one part of a balanced formula and the soap is rinsed away, many people with eczema-prone skin tolerate it well—particularly if the bar is also superfatted and enriched with soothing ingredients. If in doubt, patch test a small area and consult healthcare guidance such as the NHS advice on atopic eczema.
4. How do I know which Humble Shepherd bar to choose when the shop opens?
Once the shop is live, each bar will include clear skin-type and ingredient guidance, drawing directly on the evidence we've discussed here. In the meantime, you can read our broader overview in The Benefits of Choosing Handmade Soap and Building a Simple Daily Skincare Routine with Natural Products.
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