Scientists do not fully understand why the different types of hair growth have Straight Hair, Curly Hair, Wavy Hair, Greasy Hair or Dry Hair. This is probably determined by several factors, which may vary in their importance during life. This is why some curly-headed children have straight hair later in life, and vice versa. These factors include:
In Asian people the keratin bundles in the hair are all straight. The hair shaft tends to be thick, and almost completely round.
The keratin bundles in the hair of Caucasoid people are a mixture: most are straight, some are wavy. The proportions of the two types vary a lot. The hair shaft is usually oval in shape.
The tightly curled hair of African people twists much more frequently than in the other groups. The hair shafts are markedly oval in shape, with definite edges. The cuticle is sharply kinked at the edges, and is especially easily damaged at these points. This curious shape is the reason for the vulnerability of African hair to all forms of physical and chemical trauma, and its consequent need for extreme care in handling and very thorough conditioning.
Straight hair sometimes becomes quite wavy when damp, and wavy hair may become straight when thoroughly doused with water - in a swimming pool, for instance. This is because in these conditions great numbers of hydrogen bonds have been broken. The effect is very temporary, and the hair recovers on drying
- The way the large bundles of keratin are arranged within each hair shaft
- The position of the hair bulb in the hair follicle - in African hair the bulb may lie to the side of the follicle, and so the hair shaft grows out of the follicle at an acute angle
- Irregular growth in the hair bulb - if it varies slightly to one side or the other the hair may grow wavy
- The shape of the hair follicle, whether it is straight or curved
- The number of twists per unit length
In Asian people the keratin bundles in the hair are all straight. The hair shaft tends to be thick, and almost completely round.
The keratin bundles in the hair of Caucasoid people are a mixture: most are straight, some are wavy. The proportions of the two types vary a lot. The hair shaft is usually oval in shape.
The tightly curled hair of African people twists much more frequently than in the other groups. The hair shafts are markedly oval in shape, with definite edges. The cuticle is sharply kinked at the edges, and is especially easily damaged at these points. This curious shape is the reason for the vulnerability of African hair to all forms of physical and chemical trauma, and its consequent need for extreme care in handling and very thorough conditioning.
Straight hair sometimes becomes quite wavy when damp, and wavy hair may become straight when thoroughly doused with water - in a swimming pool, for instance. This is because in these conditions great numbers of hydrogen bonds have been broken. The effect is very temporary, and the hair recovers on drying