The number of hairs on a human head varies significantly from person to person, influenced by biological factors. This exploration delves into the typical hair count and the elements that shape individual differences.
Average Hair Count
The average human head typically holds between 90,000 and 150,000 hairs. This broad range reflects significant individual variation. Research indicates the scalp contains approximately 100,000 hair follicles, the tiny structures from which hairs grow. These figures are dynamic, as hair is constantly growing and shedding.
Factors Influencing Hair Density
Hair density, referring to the number of hair strands per square inch of the scalp, is largely determined by genetics. Genetic factors play a significant role in dictating the number of hair follicles a person is born with, which directly impacts their overall hair density. Specific genes, such as EDAR, SPRY1, RSPO1, and NRP2, have been linked to hair density and follicle development.
Ethnicity is another factor influencing hair density. Individuals of Caucasian descent tend to have the highest hair density, with averages ranging from 214 to 230 hairs per square centimeter. Asian hair typically falls in a mid-range, while people of African descent often have the lowest hair density, ranging from 148 to 160 hairs per square centimeter.
Hair color also correlates with hair count:
- Blondes generally possess the most hairs, averaging around 150,000 strands.
- Those with brown hair typically have about 110,000 strands.
- Black hair is around 100,000 strands.
- Redheads usually have the fewest, with approximately 90,000 hairs.
Beyond these inherent traits, age also plays a role, as hair density can naturally decrease over time, with hair follicles potentially stopping new hair production.
Defining “Thick Hair”
The term “thick hair” can refer to two distinct characteristics: hair density and the diameter of individual hair strands. Hair density describes the sheer number of hair strands on the scalp. Conversely, hair thickness or diameter refers to the width of each individual hair strand. A person can have a high number of fine individual hair strands, which contributes to density, or fewer, but very thick, individual strands.
The diameter of a human hair strand can range significantly, typically between 0.03mm and 0.06mm, though some can be as thick as 0.08mm to 0.2mm. For instance, Asian hair often has the largest diameter, making individual strands feel coarser. Caucasian hair is generally thinner than Asian hair, while African hair can be the finest in diameter. Therefore, someone might perceive their hair as “thick” due to a high overall number of hairs, even if each strand is fine, or because they have fewer, but notably wide, hair strands.
The Hair Growth Cycle
The number of hairs on a human head is not static; it constantly fluctuates due to the natural hair growth cycle. Each hair follicle undergoes a continuous cycle comprising three main phases: anagen (growth), catagen (transition), and telogen (resting/shedding). During the anagen phase, which is the longest, lasting several years, hair actively grows. The catagen phase is a brief transitional period where growth stops, followed by the telogen phase, a resting stage before the hair is shed.
A final phase, exogen, represents the actual shedding of old hair as new hair begins to grow. On average, a person sheds between 50 to 100 hairs daily as part of this normal cycle. This constant renewal ensures that while some hairs are shed, new ones are always emerging, maintaining a relatively consistent hair count for most individuals.