Olive Oil

Overview

Olive oil is pressed from the fruit (not the seed) of the olive tree (Olea europaea). It is the oldest cosmetic oil in continuous use in the Mediterranean basin — its presence in Greek, Roman, and Andalusian skincare goes back literal millennia.

For DIY, the key thing to know is that “olive oil” is not one product. The grades differ significantly:

• Extra virgin olive oil — first cold press, peppery and green, beautiful for cooking, often overkill for cosmetics. Strong color and scent carry through.
• Virgin olive oil — second-tier cold press, milder.
• Pomace olive oil — extracted with solvents from the residue after pressing. Pale yellow, almost no scent, much cheaper. This is the grade most DIY soap-makers and lotion-makers actually want.
• Refined olive oil — bleached and deodorized; similar to pomace, sometimes interchangeable.

Shelf life is around 1-2 years for cosmetic-grade olive stored cool, dark, and dry. Pomace tends to keep longer than extra virgin because the natural plant compounds that turn fragrant also turn rancid.

What it does in a formula

Olive oil is roughly 60-80% oleic acid, 10-20% palmitic acid, 5-15% linoleic acid, with smaller amounts of stearic and palmitoleic. It is heavily oleic-dominant — that gives it a rich, slow-absorbing, slightly heavy feel on the skin. It is genuinely conditioning, leaves a clear emollient film, and is famously gentle.

In soap-making, olive oil is the basis of true Castile soap (technically 100% olive). Castile bars cure slowly, lather modestly, and give a creamy rather than bubbly wash. SAP value is roughly 0.134 NaOH.

How to use

Add to the oil phase. Heat-tolerant; standard heat-and-hold at 75 C is fine. Pomace and refined olive oil are stable enough to add at high temperatures without concern; extra virgin should ideally be added at cool-down to preserve polyphenols, though most DIYers do not bother because cosmetic effects are similar either way.

Usage rates by product type:

• Cold-process soap: 30-100% (Castile is 100% olive; mixed bars often have 30-50%)
• Body lotions and creams: 5-20%
• Body and massage oils: 30-100%
• Body butters: 5-20%
• Hair masks and pre-shampoo treatments: 10-50%
• Face creams: 3-10% (works for dry skin; can feel heavy on combination)

Best for / Worst for

Best for: Castile and traditional Mediterranean soap, dry and very dry skin, rich body lotions, hair masks, mature skin, classic massage oils, eczema-prone skin, baby-care formulas (it is well tolerated).

Worst for: oily and acne-prone face skin (it is heavy and can feel occlusive), light summer creams, ultra-fast-absorbing formulas, anything where the soft greenish tint of cold-pressed grades would be a problem.

Common pitfalls

Using extra virgin in skincare. Extra virgin olive oil is wonderful in food but its strong color, peppery polyphenols, and higher cost are wasted in lotion bases. Buy pomace or refined cosmetic-grade unless the recipe specifically calls for extra virgin.

Authenticity issues. “Olive oil” is one of the most adulterated commodities globally — many supermarket bottles are blended with cheaper oils. For soap-making this matters less because the saponification rounds things out, but for serums and face oils, buy from a reputable cosmetic supplier.

Soap bars going off. Cured Castile soap is slow to harden — give it 4-6 weeks minimum, ideally 3 months, before using. A bar made and tested at week one will feel slimy and soft.

Comedogenicity. Olive oil is rated 2-3 on the DIY comedogenicity scale. Many people use it on the face without issue; some find it triggers congestion. Patch-test on facial skin before committing.

Substitutes

• Avocado oil — similar richness, similar oleic load, more unsaponifiables, more expensive.
• Rice bran oil — similar in soap performance, lighter on skin, very stable.
• Sweet almond oil — lighter feel, slightly more linoleic, cleaner sensory profile.
• Apricot kernel oil — much lighter; not a soap-base swap, but a face-cream swap.