Everyone has a unique hair shape and texture. Some people have very straight hair, while others have curly hair that looks like they’ve had a perm. Even after straightening your hair at the salon, the curls return after a while because each person’s natural hair is slightly different. But what causes this difference in hair shape among people?
Why does hair shape vary between individuals?
The difference in hair shape among individuals is due to the hair follicle. Hair grows from follicles, and their shape varies from person to person. The follicle is an organ that produces hair in the dermis layer under the skin. A round follicle opening produces straight hair, and an oval follicle opening makes curvy hair. Oval follicles have a twisted inner shape; because of this, the fibrous protein keratin that makes up the surface of the hair grows in a twisted arrangement, resulting in curly hair.
The shape of the inner root sheath is genetic
The shape of the inner root sheath, located at the very bottom of the hair follicle, is determined by genetics. It often depends on ethnicity, with over 95% of Africans having curly hair, which tends to be very curly. Europeans and Asians have a lower percentage of curly hair, around 12-13%, and the curls are weak. However, the proportion of semi-curly hair is higher, which is a characteristic.
Curly hair is drier than straight hair
Your hair gets greasy easily due to the sebum from your scalp. Sebaceous glands are mainly located around the hair follicles, and because straight hair is straight, sebum easily sticks to it. However, because curly hair is twisted, sebum is not easy to spread evenly throughout the hair. Not only visually, but you can also feel that curly hair is much drier than straight hair when you touch it.
Why curly hair dries faster than straight hair
When drying your hair, curly hair dries faster than straight hair. This is due to the different cuticles of each hair type. Cuticles are the epidermal layer surrounding the hair surface and have a flat structure similar to a fence. Straight hair has larger cuticles and wider gaps than curly hair. This means that the cuticles contain more moisture, so it takes longer for the moisture to escape than it does for curly hair. If you frequently perm or dye your hair, the hair can become dull, brittle, and easily breakable. This is a phenomenon that occurs when the cuticle is damaged.
Why does curly hair look frizzy?
Straight hair appears shiny because its surface is uniform and reflects light equally, while curly hair appears frizzier because of its uneven light refraction rate. If that’s the case, is having a flat cuticle layer the only factor that makes the hair look shiny? For hair to appear shiny, it’s not just about the cuticles being neatly arranged; the role of methyl eicosanoids, a fatty acid that wraps around the cuticles, is also essential. This fatty acid wraps around the hair, causing it to shine, and it is susceptible to friction or heat, so it can be lost due to shampoo, hair dryers, combing, UV rays, etc. Therefore, even if it’s straight hair, if the fatty acid that protects the cuticles is lost due to external factors, it can lose its shine.
Various types of curly hair
Curly hair, which is strongly influenced by genetics, can be divided into four types depending on the type. Wavy hair refers to curly hair with a large curl and an oval cross-section. Spiral hair has twisted hair that is not uniform in thickness and feels divided. Beaded hair is shaped like several beads connected, and the hair thickness is not uniform. Kinky hair is extremely curly and is prone to major shrinkage. The hair we commonly call pigtails corresponds to spiral and beaded hair.
It can change as you age
Did you know that straight hair can turn into curly hair as you age? This is due to changes in the shape of the follicle due to aging, as well as changes in the curvature, structural characteristics, and lipid composition of the hair. Hair thickness increases after the age of 10, is thickest around the age of 40, and then thins out. The curvature of the hair increases with age, showing a curly shape, and eventually, the hair becomes thin, and the curvature becomes uneven.
Hair care gets harder as you age
Your hair becomes curly and flies away as you age, making it harder to manage. It’s good to consume enough vitamins and not change your hairstyle too often to prevent these changes. Frequent dyeing and perming can make your hair frizzier and curlier.
Armpit hair is always curly!
Armpit hair is universally curly, regardless of race or gender. Why is that? Curly hair plays a role in drying the sweat excreted from the armpits. It creates a space for air to pass through, maintaining dryness so sweat doesn’t accumulate too much. Also, when you walk or move your body, your arms move, causing friction. At this time, it protects the armpit skin, which is weaker than other areas, from getting hurt.
Is there a difference in the degree of hair loss?
Is there a difference in the possibility of hair loss depending on whether you have straight or curly hair? There is no causal relationship between hair shape and hair loss. Straight hair tends to have thinner hair strands than curly hair, but hair loss is caused by genetics or environmental factors. Thus, hair loss cannot be determined by hair shape alone. More important than hair shape is the condition of the hair or scalp or the possibility of genetics. Therefore, if you suspect you are losing hair, taking care of it in advance is good.
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