Anatomy of a hair: Hair is made of a tough protein called keratin. A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. In the hair bulb, living cells divide and grow to build the hair shaft. Blood vessels nourish the cells in the hair bulb and deliver hormones that modify hair growth and structure at different times of life.
You will hear doctors stating that hair fall is normal and losing up to 50-100 hair strands is also normal. Why is it so? Because, hair grows and is eventually shed and replaced by new hair. This occurs in three phases. The first is the anagen phase, during which cells divide rapidly at the root of the hair, pushing the hair shaft up and out. The length of this phase is measured in years, typically from 2 to 7 years. The catagen phase lasts only 2 to 3 weeks, and marks a transition from the hair follicle's active growth. Finally, during the telogen phase, the hair follicle is at rest and no new growth occurs. At the end of this phase, which lasts about 2 to 4 months, another anagen phase begins. Hair typically grows at the rate of 0.3 mm per day during the anagen phase. Baldness occurs if there is more hair shed than what is replaced and can happen due to hormonal or dietary changes. Hair loss can also result from the aging process, or the influence of hormones.
• Anagen (growth phase): Most hair is growing at any given time. Each hair spends several years in this phase.
• Catagen (transitional phase): Over a few weeks, hair growth slows and the hair follicle shrinks.
Telogen (resting phase): Over months, hair growth stops and the old hair detaches from the hair follicle. A new hair begins the growth phase, pushing the old hair out.
Hair colour is created by pigment cells producing melanin in the hair follicle. With aging, pigment cells die and hair turns gray.
• Alopecia areata: Round patches of total hair loss, usually from the scalp. The cause of alopecia is unknown; the hair usually grows back.
• Male pattern baldness: The most common type of hair loss in men. Male pattern baldness usually includes either a receding hairline, hair loss at the crown, or both.
• Female pattern baldness: In women, hair loss usually includes uniform thinning across the scalp, with a preserved hairline. The crown may be affected, but hair loss rarely proceeds to baldness as in men. See a picture of female pattern baldness.
• Dandruff (seborrheic dermatitis): Ongoing mild inflammation of the scalp, resulting in scaly skin that may be itchy and flake off. Seborrheic dermatitis may also affect the ears and face.
• Tinea capitis (ringworm): A fungal infection of the scalp, creating round patches of hair loss. Although the patches can appear in a ring shape, no worm is involved in tinea capitis.
• Trichotillomania: A mental disorder that includes the irresistible urge to pull out one's hair. The hair pulling results in patches of noticeable hair loss; its cause is unknown.
• Head lice: Tiny insects that live on the scalp and feed on blood. Preschool and elementary school-aged children and adults who live with children are most susceptible to catching head lice, which are only spread through close contact.
• Telogen effluvium: A month or two after a personal shock (such as surgery, childbirth, severe stress), hair can abruptly fall out in large patches. Typically, new hair starts regrowing right away.
• Postpartum alopecia: Hair loss after delivering a baby- is a form of telogen effluvium and usually resolves without treatment.
• Folliculitis: Inflammation of hair follicles, usually due to an infection. Staphylococcus aureus is a bacteria that frequently causes folliculitis. Acne is a form of folliculitis that is caused by inflammation. This inflammation can sometimes be worsened by the bacteria propionibacterium acnes.
• Piedra (trichomycosisnodularis): Fungal infection of the hair shaft. Hard nodules made of fungus cling to hair fibers, sometimes causing hair loss.
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