Here's why:
* Hair Bulb: The hair bulb is the base of the hair follicle and is located within the skin. It contains living cells that divide and grow to form the hair shaft.
* Papilla: Within the bulb is the dermal papilla, which contains blood vessels that supply nutrients to the growing hair. The papilla also contains nerve endings and plays a role in regulating hair growth cycles.
* Matrix: The matrix is the area surrounding the papilla that contains the cells responsible for hair growth and pigmentation.
If the hair bulb (and particularly the matrix and papilla) is destroyed, the hair follicle loses its ability to generate new hair cells. This means:
* No more hair growth: The existing hair shaft may remain until it naturally falls out, but it won't be replaced with a new one.
* Permanent hair loss: Depending on the extent of the damage, the hair loss can be permanent.
Causes of hair bulb destruction:
* Certain skin conditions: Some skin diseases like lichen planopilaris or discoid lupus erythematosus can damage hair follicles.
* Trauma: Physical trauma or burns can damage the hair bulb.
* Radiation: Radiation therapy can damage hair follicles.
* Certain medications: Some medications can cause hair follicle damage as a side effect.
* Autoimmune diseases: In some autoimmune conditions, the body's immune system attacks hair follicles.
* Scarring alopecia: Conditions that cause scarring can destroy hair follicles.
In summary, a destroyed hair bulb equals no more hair growth from that follicle.