What Makes Hair Curly or Straight?

Apart from the differences in the color or length of our hair, you might also be wondering why some people have a head full of straight hair and why some have curly hair.

Maybe a scientific explanation may seem complex to fully understand why, but it is still needed for it to make sense.

In this article, understanding why we have different hair types will be made easy for you.

Table of Contents

What determines hair type?

Your hair type, whether straight, wavy, curly or kinky is largely determined by two things. The shape of your follicles and genes. Below, it is explained further.

The shape of your follicles

Hair follicles are pores within your skin which hair sticks out from. It is located at the top two layers of your skin and controls the growth of your hair. A damaged hair follicle can discontinue the growth of your hair.

The shape of these follicles is part of what greatly determines if your hair will be straight, wavy, curly or coily.

If the shape of your hair follicle is round, your hair will come out straight. Oval shaped follicles on the other hand grow curly hair.

Other hair types, coily and wavy hair, usually get shaped in that pattern due to a flat-oval or elliptical follicle shape.

Genes

Just like most people would have guessed, the type of hair you have is also determined by genes. These genes also contribute to how your hair follicles will be shaped. Which in turn leads to producing your hair strands according to how your follicles are shaped.

That is, when both parents both have straight hair, the offspring will have straight hair. Same for curly hair.

However, when one parent has curly hair, and the other, straight hair, something interesting happens. Curly hair has an autosomal dominant trait and according to studies, it is 85 to 95% heritable. So, the offspring has a higher chance of getting curly hair than straight hair, or somewhere in between (wavy hair).

Can your hair type change?

Yes, it can. However this change is influenced by several factors. Some permanent and some temporary. And some that can be controlled and some that can’t. The following are instances when your hair can change its texture.

When it is wet

Your hair can temporarily change its texture when wet. This is caused by hydrogen bonds. Hydrogen bonds are temporary and can change when your hair is wet and back when it’s dry.

These hydrogen bonds also act up on humid days. This is because humid air has more water molecules present in the air and this can curl up your straight hair.

Chemical treatments

Chemical treatments can alter the texture of your hair. A way of altering curly hair to straight hair is by relaxing or texturizing your hair. People who alter their straight hair to curly hair often go through a chemical process called perming.

Styling tools

Just like when your hair changes texture temporarily when wet, the effects of heat styling tools are also temporary. Curling irons can be used to temporarily change your straight strands into bouncy curls. Hair straighteners on the other hand are used to straighten curly hair. It is advised to use heat protectant spray before heat application to prevent heat damage.

Hormones

Hormones can greatly affect the texture of your hair. Right from when you hit puberty and as you age, your hormones continue to influence your hair growth and texture.

During pregnancy, there is an increase in hormone levels like progesterone and estrogen. With this increase, pregnant women experience more hair growth, volume and thicker hair texture.

During menopause or immediately after childbirth, these hormone levels reduces and causes hair to thin.

Also, for females, their hair may go from straight to curly due to increase in androgens. This increase can change the shape of the hair follicles resulting in change of hair texture.

Medications

Some medications may also change your hair texture. Oftentimes, cancer treatments, also known as chemotherapy, can change the shape of hair follicles. The hair thins out before or during treatment. After treatment, when hair starts to grow again, it may grow back curly.

Tips to care for your curly or straight hair

If you have used chemical treatment to alter the texture of your hair, and in the process you experience damage, you should use hair treatments or repairing and nourishing shampoos, conditioners or hair masks.

If your hair is thinning due to increase in androgen levels due to menopause, use biotin supplements or add it to your diet to help control it.

If you just permed your straight hair, you should know that not enough oil will coat your strands and you may experience dryness. To add and retain moisture , make use of hydrating shampoos, leave-in conditioners, heat protectant sprays ( before heat application) and wear a silk or satin bonnet to sleep.