Castor Oil For Hair Growth —
What It Does To The Shaft, Not The Follicle

Castor oil is pressed from the seeds of the castor plant, Ricinus communis. Most of it is ricinoleic acid, an unusual fatty acid that makes the oil far thicker and stickier than coconut or argan oil. The seeds also contain ricin, a toxin, but it stays in the leftover seed material; cosmetic-grade oil is processed for use on skin.

Cold-pressed oil is pale and clear. Jamaican black castor oil comes from roasted seeds, which darkens it and gives it a smoky smell; it is marketed as stronger, but no study has compared the two for hair growth. It coats well and holds moisture against the surface, which explains most of what people notice.

Most claims come from social media and product labels, not from studies in people.

The hair you can see is a shaft of dead keratin. Whether a new hair grows, how thick it is and how long it stays are decided by the follicle, a living structure deep in the scalp. Anything combed through the lengths acts on the shaft, not on the follicle's cycle.

Each hair spends years growing (anagen), then rests for about three months before it falls (telogen); losing 50 to 100 hairs a day is normal. In pattern thinning the growth phase shortens and each new hair comes back finer, a change driven by hormones and genes, not by a lack of oil.

Hair that breaks less keeps more of its length, which can feel like growth. That is length retention, not new growth, and it does nothing for a widening parting or thinning crown.

Castor oil is usually mild on intact skin, but heavy use has known problems:

• Contact dermatitis. Ricinoleic acid can cause an itchy, red, flaky rash on the scalp, hairline, eyelids or lips. Try a small amount on the inner forearm first.
• Acute hair felting. Rarely, long hair suddenly mats into a hard mass after heavy use and has to be cut.
• Eye irritation. Oil running in from the lash line can sting, blur vision and redden the eye; see a doctor if it persists.
• A worse flaking scalp. Dandruff is driven by a yeast that feeds on scalp oil; dandruff and seborrhoeic dermatitis explains why oiling aggravates it.
• Breakouts along an oiled hairline and forehead.

Swallowed, castor oil is a strong laxative. It is never taken by mouth for hair, nor in pregnancy unless a doctor advises it.

An oil is a fair thing to try for dry, brittle lengths, but the wrong first step when the pattern of loss points to a medical cause. Have your scalp examined if you notice:

• sudden, heavy shedding all over, a few months after an illness, childbirth or crash diet, typical of telogen effluvium;
• round, smooth patches, or eyebrow or eyelash loss, which can point to alopecia areata;
• a red, scaly, burning or shiny scalp with lost follicle openings, which suggests scarring alopecia and usually needs a dermatology referral;
• thinning after a new medicine (do not stop it without asking the prescriber);
• hair loss with tiredness, weight change or heavy periods, which can reflect thyroid or iron problems;
• in women, a widening parting with the front hairline kept, the picture of female hair thinning, where blood tests come first.

A follicle replaced by scar tissue does not grow hair again, whatever is applied.

Once the type of loss is known, the options tested in people differ from an oil, and none can promise regrowth in every scalp.

Medicines. Minoxidil lengthens the growth phase; it is applied to the scalp, or taken as a low-dose tablet after blood pressure and heart history are checked. Finasteride lowers DHT, the hormone that shrinks susceptible follicles; it is mainly prescribed to men and must not be used by women who are or may become pregnant. Both work only while taken, and whether either suits you is decided at a consultation; hair loss medications covers side effects and monitoring.

Laser and micrografting. H2LT is a low-level laser course for follicles still present. Regenera Activa uses small samples of your own scalp for thinning, not bare, areas. How these combine is set out under hair loss treatment.