Castor Oil and Dry Eye

Key takeaways

• Castor oil is already in eye drops you can buy. It is a formulated ingredient in Refresh Optive Advanced, Refresh Optive Mega-3 and prescription Restasis, where it is sterile, pH-adjusted and made to drug manufacturing standards.
• That is not the same as the bottle of castor oil in a cupboard. The American Academy of Ophthalmology warns that castor oil is not sterile and that using it as eye drops raises the risk of a dangerous eye infection.
• Cold-pressed, organic and hexane-free describe how the oil was extracted. None of them means sterile.
• The clinical evidence for castor oil in eye disease is two small trials totalling 46 people, neither longer than four weeks. Against roughly 26,000 US searches a month.
• Applying it to the eyelid skin, rather than into the eye, has one promising 26-person trial and a larger trial underway. That is the version with something behind it.

Three different questions, constantly confused

Almost all the confusion about castor oil and eyes comes from treating these as one topic when they are three:

1. Castor oil as an ingredient inside a manufactured eye drop.
2. Castor oil applied to the eyelid skin and lash line.
3. Castor oil from a cosmetic or food-grade bottle, dropped into the eye.

The evidence is completely different for each. Taking them one at a time is the only way to get a straight answer.

Castor oil is already in the drops on the shelf

This surprises people who have only encountered castor oil as a home remedy. It appears on the ingredient lists of real, regulated eye products:

• Refresh Optive Advanced lists castor oil among its inactive ingredients, alongside boric acid, carbomer, erythritol, levocarnitine and sodium hydroxide.
• Refresh Optive Mega-3, a preservative-free drop, lists castor oil together with flaxseed oil and trehalose.
• Restasis, a prescription cyclosporine emulsion, lists castor oil among its inactives.

Worth noting what castor oil is doing there. On all of these labels it is an inactive ingredient. It is part of how the product is built, not the thing the product is labelled to do. The international dry eye consensus report, TFOS DEWS II, mentions castor oil once, in a list of lipids used in artificial tear formulations, with no recommendation attached to it.

One product gets cited in these discussions that should not be: Cequa contains polyoxyl 40 hydrogenated castor oil, which is a chemically modified surfactant derived from castor oil, not castor oil.

What happens when people put the bottle version in their eyes

This is the practice the Academy of Ophthalmology addresses directly, and its wording is unusually blunt for a consumer page:

"Castor oil is another popular remedy for different eye conditions, such as 'dissolving' cataracts or curing eye floaters. However, there is no scientific evidence to support these claims. In fact, putting castor oil directly on the eyes can cause irritation and damage the clear, dome-shaped cornea. And because castor oil is not sterile, using it as eye drops will raise your risk of a dangerous eye infection."

Asked specifically about cold-pressed castor oil, an Academy ophthalmologist answered: "I currently do not recommend the use of any non-sterile materials in the eye."

There is also a measurement, from the Cosmetic Ingredient Review's safety assessment of castor oil, which is not widely quoted. It records that in one study of nine patients, instilling a castor oil solution produced "mild and transient discomfort and minor epithelial changes", and that "in another study involving 100 patients, the instillation of castor oil produced corneal epithelial cell death and continuity breaks in the epithelium".

That 100-patient figure is larger than either of the positive castor oil trials discussed below. It deserves the same weight.

The words on the bottle do not mean what people think

Shoppers are told to look for cold-pressed, organic and hexane-free. All three describe how the oil was pressed or extracted. None of them says anything about sterility, and sterility is the property that matters when something goes on the eye.

The manufactured drops listed earlier are sterile, buffered to a tolerable pH, made isotonic, and either preserved or packaged in single-use form, under drug manufacturing requirements. A cosmetic-grade oil has none of those guarantees however it was pressed.

We should be even-handed about one scare in the other direction. Castor beans contain ricin, and castor oil does not: the Cosmetic Ingredient Review states that ricin does not partition into the oil. Ricin is not the reason to be careful here.

Applying it to the eyelids, which is a different question

Putting oil on the skin of the lid margin is not the same as putting it in the eye, and this is where the more interesting evidence sits.

A 2021 trial in The Ocular Surface enrolled 26 people with blepharitis, who applied a cold-pressed castor oil formulation to the lids of one eye twice daily for four weeks, with the other eye as the control. Symptom scores fell significantly, and the authors reported improvements in lid margin thickening, telangiectasia, eyelash matting, madarosis, cylindrical dandruff and lid wiper epitheliopathy. No adverse events were reported.

Read that at its real size. Twenty-six people. Four weeks. One centre. A mean age of 38, which is well below the age at which most people arrive at dry eye. Using the fellow eye as a control means nobody could be fully unaware of which eye was treated. It is a promising pilot, not a settled question.

A larger trial is underway at the University of Auckland, aiming for 92 participants. One thing to watch when its results appear: the product tested combines cold-pressed castor oil with manuka and kanuka oils, so a positive result will not be attributable to castor oil alone.

The study everyone cites, and what it actually used

Almost every article arguing that castor oil works points to a 2002 study from Japan. It is a good study, and it is not evidence for what it is used to support.

It was a randomised, double-masked, placebo-controlled crossover trial in 20 patients with obstructive meibomian gland dysfunction, over two-week periods. Tear break-up time was longer on the active drops than on placebo, and several other measures improved. The authors concluded that the drops were effective and safe in that setting.

The drop they used was made for the study: 2 percent castor oil, 5 percent polyoxyethylene castor oil as an emulsifier, sodium chloride, potassium chloride and boric acid in distilled water. It was an emulsified, buffered, laboratory-prepared ophthalmic formulation. It was not castor oil out of a bottle, and the study does not tell you what happens when you use castor oil out of a bottle.

The lash growth question

This is why most people buy castor oil in the first place. Searches for castor oil and eyelashes run at roughly 22,000 a month in the United States, more than twenty times the dry eye query.

There are no clinical trials looking at castor oil and eyelash growth. The proposed mechanism is theoretical.

For a dry eye reader there is a more specific concern, and it is not about whether it works. The meibomian glands, which produce the oil layer of your tear film, open along the lash line. That is exactly where people are told to paint oil every night. We did not find a study showing castor oil obstructs those glands, so we are not claiming one exists, but it is a reasonable thing to raise with your eye doctor before starting a nightly routine on the lid margin, particularly if you already have gland dysfunction.

Dermatology-reviewed consumer guidance lists eye irritation, clogged pores or styes, and allergic reactions among the risks.

Contact lenses

The two prescription products containing castor oil both instruct lens removal. Restasis: "RESTASIS should not be administered while wearing contact lenses... Lenses may be reinserted 15 minutes following administration." Cequa carries an equivalent instruction.

Be careful with that fact. Neither label attributes the restriction to the castor oil component, so it is not evidence that castor oil and lenses conflict. The over-the-counter drops containing castor oil carry no contact lens statement at all on their labels.

Where this leaves you

If you want the benefits attributed to castor oil in a form that has been sterilised, buffered and manufactured to a standard, that already exists and it is on our shelves as Refresh Optive Advanced and Refresh Optive Mega-3.

If you are considering applying it to your eyelid skin, that is the version with real, if early, evidence behind it, and it is worth raising at your next exam rather than starting from a social media video. Your eye doctor can tell you whether lid margin disease is actually what you have.

Putting cosmetic castor oil into your eye is the one we would steer you away from, and not on general principle. It is not sterile, an expert body says plainly that it raises infection risk, and the largest set of people ever studied for it showed corneal epithelial damage.

Frequently asked questions

Is castor oil safe to put in your eyes?

The American Academy of Ophthalmology advises against it, stating that castor oil is not sterile and that using it as eye drops raises the risk of a dangerous eye infection, and that it can irritate and damage the cornea. A safety assessment also records corneal epithelial cell death in a study where castor oil was instilled into the eyes of 100 patients.

But castor oil is in real eye drops, so why not use it directly?

Because the product around it is the point. In Refresh Optive Advanced, Refresh Optive Mega-3 and Restasis, castor oil is one component of a sterile, pH-adjusted, isotonic formulation made under drug manufacturing rules. A cosmetic bottle has none of that.

Does cold-pressed or hexane-free castor oil make it safe?

No. Those terms describe extraction, not sterility. Asked about cold-pressed castor oil specifically, an Academy ophthalmologist answered that they do not recommend the use of any non-sterile materials in the eye.

Does castor oil help meibomian gland dysfunction?

A 2002 randomised crossover trial in 20 patients found improvements using a laboratory-prepared 2 percent castor oil emulsion drop over two weeks. That result belongs to that formulation. It has not been replicated at scale and it does not transfer to bottle castor oil.

Can I put castor oil on my eyelids?

One 26-person, four-week trial applying cold-pressed castor oil to the lids reported improved symptoms and lid signs with no adverse events reported. It is a small early study in a relatively young group. Ask your eye doctor, particularly if you have meibomian gland dysfunction, since the glands open along the lash line.

Does castor oil dissolve cataracts or cure floaters?

No. The Academy of Ophthalmology names both of these as popular claims and states there is no scientific evidence to support them.

Does castor oil grow eyelashes?

There are no clinical trials specifically looking at castor oil and eyelash growth.

Is castor oil poisonous because of ricin?

No. Ricin does not partition into the oil, so castor oil does not contain it.

Can I use castor oil with contact lenses?

The two prescription eye products containing castor oil both require lenses to be removed and reinserted 15 minutes later, though neither label attributes that to the castor oil. The over-the-counter drops containing it carry no contact lens instruction.

Sources

1. DailyMed Drug Facts and prescribing information, National Library of Medicine: Refresh Optive Advanced, Refresh Optive Mega-3, Restasis, Cequa.
2. American Academy of Ophthalmology. Scariest Eye Remedies on the Internet, 19 September 2023.
3. American Academy of Ophthalmology. Ask an Ophthalmologist: Is it safe to put cold-pressed castor oil in my eyes? 14 March 2022.
4. Cosmetic Ingredient Review Expert Panel. Safety Assessment of Ricinus Communis (Castor) Seed Oil and related ingredients, 2007.
5. Goto E, Shimazaki J, Monden Y, et al. Low-concentration homogenized castor oil eye drops for noninflamed obstructive meibomian gland dysfunction. Ophthalmology. 2002;109:2030-2035.
6. Muntz A, Sandford E, Claassen M, et al. Randomized trial of topical periocular castor oil treatment for blepharitis. The Ocular Surface. 2021.
7. Sandford EC, Muntz A, Craig JP. Therapeutic potential of castor oil in managing blepharitis, meibomian gland dysfunction and dry eye. Clinical and Experimental Optometry. 2021.
8. Jones L, Downie LE, Korb D, et al. TFOS DEWS II Management and Therapy Report. The Ocular Surface. 2017;15(3):575-628.
9. University of Auckland. Trial of cold-pressed castor oil for dry eye, announced February 2024.