Side Effects Of Castor Oil You Need To Know

I’ll say this plainly: castor oil has become one of those ingredients people slather on with total abandon because “it’s natural” and “everyone’s doing it.” Hair, lashes, eyebrows, elbows, even under the eyes. Pinterest is full of it.

But natural doesn’t mean risk-free, and thick, sticky, and highly concentrated doesn’t mean gentle. Castor oil is a genuinely useful oil with a long history, but it also has a documented list of side effects that rarely make it into the glowing before-and-after posts. Some are mild and forgettable. One is bad enough that it’s actually landed people in a dermatology clinic with hair that had to be cut off.

I’m Patri Hernández, a certified organic skincare formulator and dermocosmetic technician with a background in health coaching. I work with botanical oils like castor oil regularly, and part of that work is understanding not just what an ingredient can do, but where it can go wrong.

This post may contain affiliate links. If you buy something through one of them, I may earn a small commission at no extra cost to you. I only recommend products and ingredients I genuinely think are worth your time.

What makes castor oil behave the way it does

Castor oil comes from the seeds of the Ricinus communis plant. Roughly 90 per cent of its fatty acid content is ricinoleic acid, which is unusual. Most plant oils don’t have anywhere near that concentration of a single fatty acid.

Here’s the fact that surprises most people: the castor bean plant also produces ricin, one of the most toxic naturally occurring compounds known. The good news is that ricin is a protein that stays behind in the seed pulp during pressing. It doesn’t transfer into the oil itself, which is why properly processed castor oil is safe to use. It’s still a good reason to only ever buy from reputable suppliers, since proper processing is what keeps the two separated.

That same unusual fatty acid profile is behind both castor oil’s benefits and its problems. Ricinoleic acid gives it exceptional thickness, strong moisture-sealing ability, and, as you’ll see below, its reputation as a stimulant laxative.

Quick risk overview

Use case	Main risk	How serious is it
On skin (face, body)	Contact allergy, clogged pores	Rare, usually mild
On long hair	Acute felting or matting	Rare, but can be irreversible
Around the eyes or lashes	Irritation, clogged glands, styes	Uncommon, but avoidable
Taken orally	Cramping, diarrhoea, dehydration	Common at laxative doses
During pregnancy	Uterine stimulation	Debated, needs medical guidance

Skin reactions: rare, but real

Contact allergy to castor oil is uncommon, but it’s well documented in the dermatology literature, mostly through case reports of people reacting to castor oil in lip balms, lipsticks, and moisturisers. The Cosmetic Ingredient Review panel, which assesses the safety of cosmetic ingredients, has looked closely at castor oil and ricinoleic acid and found the data broadly reassuring, but not zero risk.

Symptoms of a genuine allergic reaction include:

• Redness, swelling, or itching where the oil was applied
• A rash that develops hours after application rather than instantly
• Persistent irritation around the lips or eyelids, which are more delicate than the skin elsewhere

A patch test matters more with castor oil than with a lot of gentler carrier oils, simply because it’s used so heavily around sensitive areas like the lash line and lips. Apply a small amount to your inner forearm, wait 48 hours, and check for any reaction before using it anywhere near your face.

The castor oil versus castor wax distinction

One detail worth knowing: several documented reactions weren’t to castor oil itself, but to hydrogenated castor oil (sometimes labelled 12-hydroxystearic acid), a wax-like derivative used in cosmetics. In at least one published case, a person reacted to castor oil but tested completely clear for castor wax. If you’ve had a past reaction to a “castor” ingredient, it’s worth checking exactly which form it was, since they aren’t interchangeable.

I’d also flag something a lot of casual beauty content gets wrong: influencers and even some bloggers writing about “natural” ingredients often don’t have formal training in dermatology, cosmetic chemistry, or the relevant research literature. That matters, because “I’ve never had a reaction” is not the same thing as “this is universally safe.”

The hair side effect almost nobody mentions: felting

This is the one that genuinely surprises people, and it’s worth taking seriously.

Acute hair felting, sometimes called matting, is a rare but documented reaction to castor oil, particularly on long hair. Dermatology case reports describe hair that twists, curls, and tangles into a dense, stony mass within hours of applying castor oil and then drying or towelling the hair. Once it’s happened, it’s not something you can comb out. The hair usually has to be cut.

In the original published case, a young woman’s hair matted so severely after a single castor oil hair wash that its length was reduced by half by the time she reached the clinic. It happened to healthy hair with no prior damage. The oil’s thickness combined with the friction of towel-drying was enough on its own.

This happens because castor oil is exceptionally viscous. When it coats long strands and then meets friction, from towel-drying, sleeping, or brushing before it’s properly rinsed out, the fibres can bind together in a way lighter oils simply don’t.

To reduce this risk:

• Use less than you think you need. A little goes a long way with an oil this thick.
• Avoid applying it to very long hair without diluting it in a lighter carrier oil.
• Wash it out thoroughly rather than leaving heavy amounts in overnight, especially the first few times you use it.
• Be gentle when detangling wet, oiled hair. Don’t rub or twist.

If you’re building out a castor oil hair routine, it’s worth reading my guide to natural hair growth tips alongside this one, since a lot of the same “less is more” principles apply.

Scalp buildup and the breakout question

Castor oil isn’t classed as strongly comedogenic, but it is heavy and occlusive. Used too often, or in too generous a quantity, it can sit on the scalp and skin, trap sweat, dead skin cells, and product residue, and contribute to clogged follicles or a greasy, flaky scalp.

This isn’t the same thing as “purging,” a term that gets thrown around loosely online. True purging is a specific, temporary reaction to actives like retinoids that speed up cell turnover. Castor oil doesn’t do that. If your skin breaks out after using it, that’s much more likely to be a straightforward case of the oil being too heavy for your skin type, or of buildup from insufficient cleansing, rather than some deeper “detox” process.

If you notice congestion, cut back frequency before assuming it’s temporary.

Eye and eyelash side effects

Castor oil on the lash line is genuinely popular, and dermatologists and ophthalmologists have been vocal about the risks that come with it.

The main concerns are:

• Contamination. Most cosmetic-grade castor oil isn’t sterile, and repeatedly dipping a wand or fingertip into the bottle introduces bacteria over time.
• Clogged meibomian glands. These tiny glands along the eyelid margin produce the oily layer of your tears. A thick oil applied too close to them can block them, which can worsen dry eye or contribute to styes.
• Direct eye irritation. If castor oil gets into the eye itself, it can cause stinging, redness, or temporarily blurred vision.

Here’s the part that tends to surprise people: castor oil genuinely does have a legitimate medical use for the eyes. It’s included in some prescription-strength artificial tears because it helps stabilise the tear film’s oily layer. The catch is that those formulations are sterile, purified, and precisely dosed, which is a world away from dipping a mascara wand into a bottle from the bathroom cabinet.

The American Academy of Ophthalmology has specifically pushed back on the social media trend of applying castor oil around and on the eye, noting there’s very limited quality evidence behind claims that it treats floaters, cataracts, or blurry vision, and that sterile, purpose-made products are the safer route for anything actually going near the eye itself.

If you do use it on your lashes, apply with a clean, single-use applicator rather than a shared wand, keep it to the lash tips rather than the lash line itself, and stop immediately if you notice any redness or grittiness.

Oral use: the side effects people underestimate

Castor oil is an FDA-recognised stimulant laxative, and this is where a lot of the more serious side effects show up, because taking it internally is a different proposition entirely from applying it to skin or hair.

Common reactions to oral castor oil include:

• Abdominal cramping and nausea
• Diarrhoea, sometimes severe
• Dehydration and electrolyte imbalance with repeated or excessive use
• Dizziness or fatigue

Oral castor oil is not something to self-dose casually or use regularly. It’s a strong stimulant laxative, not a gentle wellness tonic, and using it frequently can disrupt your body’s normal bowel function and fluid balance.

Castor oil and pregnancy

You may have come across the old idea of using castor oil to induce labour. The research here is genuinely mixed rather than settled. Some studies, including a 2022 systematic review and meta-analysis, found it increased the likelihood of labour starting without serious harm in the study populations. Other trials found no meaningful effect at all, and clinical guidelines still don’t formally recommend it, largely because dosing varies wildly between studies and side effects such as nausea, vomiting, and meconium-stained amniotic fluid have shown up in several of them.

One nuance worth knowing: several studies found castor oil worked noticeably better at encouraging labour in women who had already given birth before, compared with first-time mothers. It’s a good example of why “it worked for my friend” isn’t the same as it being predictably effective, or safe, for you.

This isn’t a decision to make from a blog. Anyone pregnant should only consider castor oil, in any form, after discussing it directly with their midwife or obstetrician.

Who should be more cautious with castor oil

• People with known allergies to castor oil, ricinoleic acid, or related compounds
• Anyone with active eye conditions, styes, or blepharitis
• People with intestinal obstruction, appendicitis, or undiagnosed abdominal pain (oral use)
• Pregnant women, without medical guidance
• Anyone with very long or fine hair, who is at higher risk of matting

Reducing your risk overall

• Always patch test before your first application, especially near the face or eyes
• Choose a cold-pressed, unrefined castor oil rather than a heavily processed one
• Store it in a cool, dark place, tightly sealed, to slow oxidation
• Use it sparingly rather than heavily
• Wash it out thoroughly rather than leaving thick layers in for extended periods

A small silver lining: castor oil’s unusually high ricinoleic acid content actually makes it more resistant to going rancid than many other carrier oils, so a well-stored bottle can genuinely last longer than you’d expect. That’s a plus for your shelf, but it’s not a reason to be casual about how much you’re applying to your skin or hair.

If you want a lighter, less risky oil for everyday facial use, I’d point you towards my piece on natural thick hair remedies, which covers oils that behave rather differently to castor oil on the hair and scalp.

Frequently asked questions

Is castor oil safe for daily use on skin or hair?

For most people, yes, in small amounts. But daily heavy application increases the risk of buildup, clogged follicles, and, on long hair, matting. A few times a week is usually plenty.

Can castor oil cause hair loss?

There’s no good evidence that castor oil itself causes hair loss. The concern with hair is felting and matting from overuse, not follicle damage.

Is Jamaican black castor oil different from regular castor oil?

Yes, the roasting process used to make Jamaican black castor oil changes its pH and gives it a smokier scent, but the core fatty acid profile, including its thickness and its potential for reactions, is largely the same.

Can I use castor oil if I have sensitive skin?

You can, but patch test first and start with a small amount mixed into a lighter carrier oil rather than applying it neat.

Should I stop using castor oil if I notice a reaction?

Yes. Stop immediately, wash the area gently, and avoid using castor oil again until you understand what caused the reaction.

The bottom line

Castor oil earns its reputation as a hardworking, moisturising oil, but it’s not a “the more the better” ingredient, and it isn’t without genuine, documented risks. A little goes a long way, patch testing is not optional, and anything involving your eyes or a pregnancy deserves a proper conversation with a professional rather than a Pinterest board.

Used thoughtfully, in the right amount, on the right part of the body, castor oil can absolutely earn its place in your routine. Used carelessly, it’s the kind of ingredient that can genuinely surprise you, and not in a good way.

References

• Cosmetic Ingredient Review: Safety Assessment of Ricinus Communis (Castor) Seed Oil
• International Journal of Trichology: “Castor Oil” – The Culprit of Acute Hair Felting
• PubMed: Allergic Contact Dermatitis from 12-Hydroxystearic Acid and Hydrogenated Castor Oil
• PMC: Effect and Safety of Castor Oil on Labor Induction and Prevalence of Vaginal Delivery, Systematic Review and Meta-Analysis
• Ophthalmology Times: Ophthalmologists warn against rubbing castor oil in the eyes

Love, Patri xx