Deep Dive

Lash serums are used to support lash durability, lash retention, and the appearance of fullness. Commercial formulas often rely on prostaglandin analogs, stabilizers, preservatives, and penetration enhancers. These inputs operate through strong biochemical pathways that can cause skin discoloration, irritation, or changes to the lash line.

Castor oil and rosemary extract appear frequently across non-commercial use because each input has a functional profile that supports the surface environment of the lash line. The focus is not on forced growth. It is on creating a stable surface, reducing breakage, and maintaining the conditions that lashes rely on.

The Commercial Version

Commercial lash serums often contain:

• prostaglandin analogs

• synthetic conditioners

• penetration enhancers

• fragrance

• stabilizers

• silicone carriers

Prostaglandin analogs are the main active. These compounds can influence pigmentation on the eyelid, alter the lash line, or lead to irritation.

The rest of the formula supports texture, shelf stability, or rapid absorption rather than contributing to functional lash support

 

The Swap

Castor oil and rosemary extract provide a simple, single-layer approach. Castor oil has a dense, slow-spreading structure that stays on the lash line, forming a consistent surface layer. Rosemary extract is used for its topical antioxidant activity. Together they create a low-interference topical environment without additional synthetic inputs.

This swap does not operate through prostaglandin pathways. It functions through surface support only.

 

What You’ll Need

• Cold-pressed castor oil

• Rosemary CO2 extract or rosemary-infused oil

• Clean spoolie or fine eyeliner brush

• Small glass vial with reducer inser

 

Packaging

Use a small glass vial with:

• dark or amber glass

• reducer insert or dropper

• tight-seal cap

Avoid plastic packaging for long-term oil storage.

 

Ingredients

Castor Oil

A dense topical oil that stays in place and maintains surface integrity along the lash line.

Rosemary Extract (CO2 or oil infusion)

Used for topical antioxidant activity on the skin surface.

Optional: Vitamin E (tocopherol)

Acts as an antioxidant to support oil stability.

 

Mixing

Combine castor oil and rosemary extract at a low ratio.

Use 1 to 2 drops of rosemary CO2 extract per tablespoon (15 ml) of castor oil.

If using a rosemary-infused oil instead of a CO2 extract, keep the ratio 1 part infused oil to 3 parts castor oil.

For rosemary CO2 extract, use one to two drops per tablespoon of castor oil.

Shake gently to distribute.

 

Application

Use a clean spoolie or fine brush.

Wipe excess before application.

Apply only to the upper lash line.

Do not apply directly to lashes or waterline.

If irritation occurs, discontinue use.

 

Suggested Use

Apply a minimal amount along the upper lash line.

Use once daily at night.

Keep the product out of the eye.

Avoid using excess oil.

 

Storage

Store in a cool, dry area.

Keep away from direct heat and sunlight.

Average shelf stability is six to twelve months depending on storage conditions.

 

DISCLAIMER

The information here reflects ingredient data, input mapping, and functional analysis. It is not medical guidance. Decisions about use rest with the individual.

All material is drawn from existing research and open data. We organize it through a clear system so users can work with inputs without carrying the analysis themselves.