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Although hair is a much studied topic some aspects still remain a mystery, including why straight hair suddenly becomes curly or vice versa. Most hair does not change drastically, although it has been known to happen. When straight hair becomes curly this suggests that something is happening to the shape of the hair follicles but no one knows why that happens or what causes it, although hormones are considered to play a role even though there is presently no evidence to confirm this.


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Our hair changes naturally as we age and particularly when we enter midlife. It becomes finer, less full and many people experience hair thinning or loss. That is to be expected but no one expects their straight hair to go curly. It remains a mystery how straight hair with a rounder follicle suddenly transforms into a flatter follicle, which creates curly hair.


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Cancer patients who have undergone chemotherapy often find that their formerly straight hair grows back in curly. This may be due to the fact that chemo has an affect on rapidly growing cells, including hair follicles. When jolted by the chemo, the follicle changes temporarily but will eventually return to its regular shape.

Muscular Changes in the Base of Hair Follicles

Changes in the muscles at the base of each hair follicle may be the reason hair textures sometimes change, according to Jonathan Torch, who is the founder of Toronto’s Curly Hair institute and the creator of Curly Hair Solutions. Muscular changes frequently occur during puberty, menopause and chemotherapy when medications and hormones alter the muscle tone of the hair follicle. Sometimes the change in hair texture can be extreme. When the muscles change in the hair follicle, Torch believes the shape of the follicle changes and causes straight hair to become curly or vice versa.

Hair Follicles Become Altered Over Time

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Not only does hair turn gray, losing its pigment as you age, but aging alters the way hair follicles grow. They don’t grow as quickly and this can make curly hair straighter. When there is slow follicle growth this prompts hair to fall out and when it does grow back in it may be coarser than it was before.