Medicinal Oils

Part of Pharmacy and Apothecary

Oil-based pharmaceutical preparations — infused oils, medicated carrier oils, and their applications for wound care, pain relief, and skin conditions.

Why This Matters

Oil-based preparations fill a specific niche in the pharmaceutical toolkit. They provide a medium for fat-soluble medicinal compounds that water cannot carry. They create an occlusive layer on skin that prevents moisture loss and protects wounds from contamination. They allow slow, sustained release of active compounds over hours. And they can be easily combined with wax to form salves and ointments of varying consistency.

Many of the most effective topical wound medicines are oil-based. St. John’s Wort oil has evidence supporting its use in nerve damage and burns. Calendula oil promotes wound healing and has antimicrobial properties. Lavender oil in an olive oil base provides both antiseptic and calming benefits. These are not folk remedies with no mechanism — the compounds responsible for their activity have been studied, and their oil solubility is the reason oil extraction is appropriate.

Beyond wound care, medicinal oils are lubricants for difficult births, ear preparations, scalp treatments for fungal infections, and bases for massage therapy. A well-stocked apothecary maintains a range of infused oils as a foundation for many preparations.

Base Oils: Selection and Properties

The carrier oil forms the bulk of any medicinal oil preparation. Its properties affect the final medicine:

Olive oil: The traditional apothecary base. Stable, relatively long shelf life (1-2 years), penetrates skin well, suitable for all skin types. Contains oleic acid which has some anti-inflammatory properties. The most practical choice when other options are unavailable.

Sunflower oil: Lighter than olive oil, absorbs into skin quickly, less residue. High in linoleic acid, which supports the skin barrier. Suitable for inflamed or sensitive skin. Shelf life similar to olive.

Linseed (flaxseed) oil: High in omega-3 fatty acids, but oxidizes rapidly — short shelf life (weeks to months) and becomes thick and sticky. Best for specific therapeutic uses requiring omega-3 content; not ideal as a general base.

Castor oil: Thick, viscous, long shelf life. Does not absorb well into skin but forms an excellent protective film. Useful for constipation (internal — 15-30 mL dose), as a scar softener, and in hair preparations. Its thickness makes it useful for mixing with thinner oils.

Tallow and lard: Animal fats that were the primary base for ointments historically. Very occlusive (good barrier function), long shelf life if rendered and stored properly, tolerated well by most skin. Tallow from beef, lard from pig. Rendered clean tallow is comparable to commercial petroleum jelly in barrier function.

Coconut oil: Solid below about 24°C, liquid above. Contains lauric acid with antifungal and some antibacterial properties. Absorbed well by skin. Reasonable shelf life. Good choice for antifungal preparations.

Making Infused Oils

Cold maceration (preferred for delicate flowers):

1. Ensure plant material is fully dried — any moisture causes rancidity
2. Fill a clean, dry jar loosely with plant material
3. Pour base oil to cover completely, filling all air spaces
4. Seal and label with date and contents
5. Place in a warm location (15-25°C) for 4-6 weeks
6. Shake or stir daily if possible
7. Strain through fine cloth, pressing firmly
8. Store in dark bottles away from heat

Warm oil infusion (faster, works well for dried material):

1. Combine plant material and oil in a double boiler
2. Maintain temperature at 50-60°C — warm but not hot (hand-test: uncomfortable but not painful)
3. Steep for 1-3 hours, stirring occasionally
4. The oil should pick up color from the plant material
5. Strain while warm, as oils thicken when cooled

Signs of spoilage: Off smell (rancid, musty, or sour), cloudiness, or visible mold (mold can grow at the oil-air interface around the stopper). Discard any preparation showing these signs.

Key Medicinal Oil Preparations

St. John’s Wort oil:

• Plant: Hypericum perforatum flowers and buds, freshly opened
• Base: olive oil
• Method: cold maceration 4-6 weeks
• Quality indicator: deep blood-red color (essential — pale oil was not properly extracted)
• Uses: nerve damage, bruises, burns, sciatica pain when massaged in
• Note: fresh flowers only; dried flowers produce much weaker extract

Calendula oil:

• Plant: Calendula officinalis flowers, fully dried
• Base: olive oil
• Method: warm infusion or cold maceration
• Quality indicator: golden-orange color, slight resinous smell
• Uses: wound healing, dry skin, mild infections, baby skin

Lavender oil (not the same as steam-distilled essential oil):

• Plant: dried lavender flowers
• Base: sunflower or olive oil
• Method: cold maceration 4 weeks
• Uses: minor wounds and burns, insect bites, relaxation massage
• Note: this is an infused oil (gentle) — different from concentrated lavender essential oil (potent)

Rosemary oil:

• Plant: dried rosemary herb
• Base: olive oil
• Method: warm infusion
• Uses: scalp and hair preparations, muscle pain massage, circulatory stimulant
• Caution: avoid in pregnancy (stimulates uterine activity at high doses)

Garlic oil (fresh preparation only):

• Plant: fresh crushed garlic
• Base: olive oil
• Method: fresh crushed garlic steeped in oil for 30 minutes maximum
• Uses: ear infections (3-4 drops warmed oil in ear, twice daily), topical antimicrobial
• Critical warning: do not store garlic-in-oil for more than 24 hours at room temperature — this is a confirmed botulism risk. Make fresh each time or refrigerate and use within 1 week.

Comfrey root oil:

• Plant: dried comfrey root (Symphytum officinale)
• Base: olive oil
• Method: warm infusion, longer (3 hours) due to hard root
• Uses: fractures, sprains, bruises — allantoin in comfrey promotes cell proliferation
• Important: apply only to unbroken skin. Do not apply over open wounds — promotes surface skin closure before deep healing, which traps infection.

Ear Oil Preparation

Warm oil in the ear canal is one of the most effective treatments for simple ear infections and pain. It softens ear wax, reduces inflammation, and if the oil contains antimicrobial compounds, treats minor infections.

1. Warm the oil to body temperature — test a drop on your inner wrist; it should feel neutral, not hot
2. Have patient tilt head to expose ear canal
3. Place 3-5 drops of warmed oil in the canal
4. Patient holds position for 5 minutes
5. Gently plug with a small piece of clean cloth
6. Repeat 2-3 times daily

Suitable oils for ear use: garlic oil (fresh), warm olive oil, mullein-garlic oil combination

Do not use ear oil if there is any possibility of a ruptured eardrum (severe pain, discharge of fluid, hearing loss following head trauma). Oil entering the middle ear causes serious additional problems.

Shelf Life and Storage

Properly made and stored infused oils last:

• Olive oil base: 6-12 months
• Sunflower oil base: 4-6 months
• Tallow/lard base: 12-24 months (most shelf-stable)
• Coconut oil base: 12-18 months

Store in cool, dark locations. Add a few drops of vitamin E oil (from wheat germ oil, which is naturally rich in it) to extend shelf life — vitamin E is a natural antioxidant.

Label every preparation: contents, date made, expiry, and concentration if known. When in doubt about age, smell before using. A rancid base oil reduces effectiveness and can irritate tissue.