What Makes Hair Curly? Follicle Shape, Genes and Care
Your curl pattern is set before a single strand reaches the surface of your scalp. The shape of the hair follicle, the tiny pocket in the skin that forms each strand, largely determines whether hair comes out straight, wavy, curly or coily. That means curls are a matter of biology, not a flaw to fix, and it explains why dermatologists recommend a gentler, more moisture-focused routine for them.
Curl starts beneath the skin
Every strand of hair is built inside a follicle, and the follicle works like a mold. According to Medical News Today, scientists know that the shape of the hair follicle and the behavior of follicle cells during hair formation both contribute to hair shape. Curly hair comes from curved follicles, described as S-shaped with two bends.
Inside a curved follicle, the cells divide and produce certain proteins unevenly, and that unevenness lines up with the bends. The result, the same article explains, is a fiber with an elliptical (oval) shape that is able to curl. A ScienceAlert report on the research describes a 2005 study that dissected human scalp follicles and found that curly hair is already curving before it leaves the skin, and a 2019 literature review concluding that follicle shape decides whether a strand emerges coiled, kinked or straight.
Straight follicles, by comparison, have more symmetrical structures, so the strand forms evenly on all sides and stays straight.
Genes and ancestry: a spectrum, not a category
Hair shape is inherited. Medical News Today reports that genes control hair shape, and the best-known example is the gene for trichohyalin (TCHH), a protein that strengthens the forming hair. Variants of TCHH are associated with different hair shapes in people around the world. A different gene, EDAR, has variants associated with straight, coarse hair in people of East Asian descent.
It is tempting to sort hair by background, but ScienceAlert notes that every population, regardless of ancestry, shows a spectrum of hair shapes, even though some curl patterns are more common in some genetic lineages than others. In practice, that is why two people in the same family can have very different textures.
Why curly hair needs a different routine
The American Academy of Dermatology (AAD) states plainly that curly hair is drier than other hair types and more prone to breakage and dryness. Its leave-in conditioner guidance adds that curly hair needs more conditioning than straight hair. The AAD pages do not explain the reason, so we will not guess at a mechanism here. What they do offer is practical, dermatologist-backed guidance.
What dermatologists recommend for curls
The AAD's curly hair care tips and its list of habits that damage hair add up to a simple routine:
Wash only when needed. The AAD says curly hair does not need to be washed daily or even weekly, and recommends washing long or dense hair in sections to reduce tangling.
Choose a moisturizing shampoo formulated for curly hair, and condition all of your hair, not just the ends. For conditioners, the AAD suggests looking for ingredients such as argan oil, glycerin, or a fatty alcohol like cetyl or stearyl alcohol.
Detangle gently. For tight curls, the AAD advises combing while the hair is damp with a wide-tooth comb, and between washes, applying a leave-in conditioner and using your fingers or a wide-tooth comb or brush designed for curly or coily hair. Avoid brushing dry hair.
Go easy on heat and sun. The AAD notes that heat and ultraviolet rays can dry out curly hair, and suggests a wide-brimmed hat outdoors and the lowest heat setting when you do style with heat.
Reduce friction overnight. A loose ponytail on top of the head (the "pineapple") or a loose braid can reduce rubbing against the pillowcase, according to the AAD.
Tools for detangling and nighttime
Because the routine above leans on gentle detangling and a low-tension nighttime setup, a few simple tools can make it easier to follow.
For wash-day and between-wash detangling sessions, the QOH shop carries the Crown Care Detangling Hair Brush.
For bedtime, there is also the Silky Long Satin Bonnet, a satin sleeping cap.
What is not proven
Researchers still do not fully understand how the follicle produces every variation of twist, kink and wave; Medical News Today notes that this exact mechanism had eluded scientists as of its 2017 article. The sources above describe curl pattern as set by follicle shape and genetics, and none of them describes a hair product that changes it. Good care can keep curls comfortable and conditioned, but it does not alter the pattern your follicles create. If you notice new dryness, flaking, soreness or changes in your scalp or hair, a dermatologist can look at your individual situation.
Sources
Medical News Today: Curly or straight: What determines hair shape?
ScienceAlert: Scientists Finally Worked Out Why Some Hair Is Curly
American Academy of Dermatology: 6 curly hair care tips from dermatologists
American Academy of Dermatology: 10 hair care habits that can damage your hair
American Academy of Dermatology: Dermatologists' top tips for using leave-in conditioner
This article is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any condition. Talk with a qualified healthcare provider about skin or scalp concerns.
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