We grow hairs anywhere in our body except in the soles and palms. Although most of them are not visible, we actually grow the same amount of hair as gorillas do. Hair is made of the protein called high-sulfur keratin, which gives the hair elasticity and shape. Naturally curly hair has less keratin compared to naturally straight hair. Furthermore, depending on their location, hair differ in length and cycling.
Follicles are the structures at the base of every hair strand that produce hair. In the follicle, newly keratinized cells push out old ones to form part of the hair strand at a rate of about ½ inch per month. The hair that we see in the surface are actually made up of old keratinized cells. In an adult human scalp, there is at least 100,000 hair follicles. Every day, we lose an average of 50-100 hair strands as a part of the hair renewal process. Specifically, our hair undergoes three distinct phases at any one time.
Hair Growth Cycle
Anagen Phase
During the anagen phase, the keratinized cells at the roots multiply rapidly, that is at a faster rate than the rest of the cells in the body. Approximately 90% of the hair in the scalp is undergoing anagen phase which lasts from three to five years. Each month, the average growth of the hair is about one and a half inch.
Catagen Phase
During the catagen phase, at least one percent of the hair stops growing. This is because the hair follicle miniaturized and comes off from the dermal papilla. This transition could last for one to two weeks.
Telogen Phase
This is when the hair finally dislodges from the follicle to be replaced by a new one. Approximately 10 percent of the hair in the scalp is in the telogen phase, which could last for 2-3 months.
Hair growth is fastest between ages 15-30. It slows down as we age. Moreover, it can be lost due to unnatural reasons. Hair loss/thinning or balding affects people of all ages. Hair loss or technically known as alopecia takes several forms, depending on the cause. There are patchy types of hair loss, total baldness as well as diffuse types. Types of alopecia include:
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Androgenetic Alopecia
This condition is believed to be a result of genetics and male hormones. It affects both men and women. AGA occurs when the enzyme 5-alpha reductase metabolizes testosterone to produce dihydrotestosterone (DHT) that attacks the the hair follicles. DHT build-up blocks the nutrients that flow to the hair follicles, causing the follicles to miniaturize and eventually die if left untreated.
Traction Alopecia
Traction alopecia is a result of harsh hair styling like wearing tight ponytails, braids overtime. These habits cause too much stress on the hair resulting it to break. Traction alopecia is quite common in African-American women who are fond of hair grooming. Although this is a less serious type of hair loss, traction alopecia tends to be permanent if left untreated.
Alopecia Areata
Alopecia areata is characterized by patches of hair loss anywhere in the body. Alopecia areata is believed to be triggered by an abnormality in the immune system. The immune system attacks the hair follicles to die. This condition is only temporary yet the accurate reason remains vague.
Telogen Effluvium
Telogen effluvium is another common yet temporary hair loss that mostly affect women. This happens when excessive stress, traumatic childbirth or such other temporary factors induces hair to enter the resting phase prematurely, thus reversing the normal hair growth cycle. Usually, it occurs 6 weeks to 12 weeks after the stressful event.
Trichotillomania
Trichotillomania is a mental disorder of pulling the hair from the scalp or from any part of their bodies. People with this compulsive behavior find pleasure in pulling their hair.
