It's a common occurrence to have curly hair underneath and straight on top, and many people wonder why this happens. Although the exact reason for this hair phenomenon is not fully understood, there are a few scientific explanations that can shed some light on this hair characteristic.
One of the primary reasons for curly hair underneath and straight on top is genetics. Hair texture and curl pattern are determined by the shape of the hair follicle. Follicles that are more oval or asymmetrical tend to produce curly hair, while round follicles produce straight hair. It is possible that the hair follicles on the top of your head are more round, while the follicles on the underside of your hair are more oval or asymmetrical, resulting in curly hair.
Another explanation for curly hair on the underside is the angle of hair growth. Hair grows out of the scalp at an angle, and the angle of growth can affect the hair texture. Hair that grows at a sharp angle tends to curl, while hair that grows straight out of the scalp will remain straight. It's possible that hair on the back of your head grows at a sharper angle, causing it to be curlier, while the hair on the top of your head grows straighter.
The thickness and density of your hair can also affect its curl pattern. Thicker hair tends to be curlier because it has more weight and volume, which can create more defined curls. Hair that is thinner and less dense will appear straighter. It's possible that the hair on top of your head is thinner and less dense, causing it to be straighter, while the hair on the bottom is thicker and denser, resulting in more curl.
While you can't change the shape of your hair follicles, you can alter the appearance of your curls with styling products and techniques. For example, using a diffuser when blow-drying or scrunching your hair can enhance your curls. There are also chemical treatments, such as perms, that can permanently change your hair's texture.
Curly hair can require more maintenance than straight hair, regardless of where it is located on your head. However, the underside of your hair may be more prone to tangles and knots due to friction with clothing and bedding. Using a leave-in conditioner or detangling spray can help prevent tangles and make it easier to maintain your curls.
The texture of your hair can change over time due to hormonal fluctuations, stress, and other factors. For example, many women experience changes in their hair texture during pregnancy or menopause. However, genetics still play a significant role in determining your hair texture, so any changes may be limited.
