Pourquoi avons-nous des poils au nez?

Why do we have nose and ear hair?

You have probably already asked yourself some questions about these hairs often considered unsightly in the ears or in the nose. Maybe you even decided to take them off before a date. Today, we take the fold to explain to you where they come from.

The hair growth cycle

The hair growth cycle can be broken down into three phases: anagen, catagen and telogen.

  1. Anagen: The growth phase, during which the hair shaft is continuously produced. This phase lasts from two to six years.
  2. Catagen: the transition phase during which the cells of the hair shaft die and are pushed out from the surface of the follicle. These dead cells then form a layer of tissue called squamosium.
  3. Telogen: the resting phase, during which the hair shaft is reabsorbed into the skin. The follicle remains completely quiescent for 3-4 months. A well deserved rest, shall we say.

The hair cycle then starts again.

The moment it goes wrong...

However, as we age, these steps sometimes go out of whack. Some of our hair follicles actually develop sensitivity to DHT, a byproduct of testosterone that shortens the lifespan of each affected follicle. After the DHT has caused irreversible damage, the individual begins to lose large amounts of hair. Once a person reaches a point where they are losing large amounts of hair, they usually begin to notice thinning as it is obvious that they don't have enough. This is why long-term exposure to DHT will eventually cause complete baldness. In short, here you are Dwayne Johnson, without using a razor!

Paradoxically, DHT is also responsible for a spurt of ear and nose hair growth. DHT acts like a steroid for the hair that grows out of our ears and nose, which is why it grows to surprising proportions without regular trimming as we age. Simply put, DHT causes the hair to fall out on our heads, while causing our facial hair to grow wild.

How is DHT made?

DHT is made from the conversion of testosterone and is an active metabolite of the hormone. Production can take place both in the prostate and in the hair follicles, in particular.

Now you know. And if you're wondering about the length of the hairs if you never plucked them, well... We don't know more about these hairs, but we can guide you in the answer for the beard.

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