3.2 Hair Growth Cycles, Hair Loss & Scalp Disorders

Hair Growth Cycles, Hair Loss & Scalp Disorders

Exam Focus: Virginia State Board examinations frequently test the three phases of the hair growth cycle (anagen, catagen, telogen), shedding metrics, varieties of alopecia, non-contagious scalp conditions (pityriasis), and contagious conditions (tinea, pediculosis, scabies, staph infections) that mandate immediate service refusal.

Understanding hair growth physiology and scalp pathology is essential for every practicing cosmetologist. Cosmetologists must be able to differentiate between normal hair shedding, progressive hair loss, non-contagious scalp scaling, and contagious parasitic or fungal infections.

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Hair Types: Vellus vs. Terminal Hair

Human bodies feature two main types of hair:

1. Vellus Hair (Lanugo Hair): Short, fine, unpigmented, downy hair that covers almost the entire body (except the palms of the hands and soles of the feet). Vellus hair helps regulate body temperature and evaporation of sweat.
2. Terminal Hair: Long, coarse, pigmented hair found on the scalp, legs, arms, and bodies of males and females. Terminal hair originates from hair follicles that were previously vellus follicles prior to puberty or hormonal stimulation.

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The Three Phases of the Hair Growth Cycle

Hair growth occurs in repeating cycles consisting of three main phases: Anagen, Catagen, and Telogen.

[ Hair Growth Cycle Dynamics ]
 Anagen (Growth: 2-6 yrs) --> Catagen (Transition: 1-2 wks) --> Telogen (Resting: 3-6 mos)
      ^                                                                  |
      +---------------------- New Hair Pushes Old Hair Out <-------------+

Growth Rate & Normal Shedding

• Average Scalp Growth Rate: Scalp hair grows approximately 0.5 inch (1.25 cm) per month.
• Normal Daily Shedding: The average healthy scalp sheds 50 to 100 hairs per day. Daily loss within this range is part of natural telogen shedding and does not indicate alopecia.

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Hair Loss & Alopecia Classifications

Abnormal, excessive, or premature hair loss is clinically termed alopecia. Cosmetologists must recognize the primary forms of hair loss during client consultations:

1. Androgenetic Alopecia

• Cause: A combination of genetics, age, and hormonal changes—specifically the conversion of testosterone into dihydrotestosterone (DHT), which causes progressive miniaturization of terminal hair follicles into fine vellus hair.
• Manifestation: In men, it presents as male pattern baldness (receding hairline, crown balding). In women, it presents as diffuse thinning across the entire crown (female pattern hair loss).

2. Alopecia Areata

• Cause: An autoimmune disorder in which the client's immune system mistakenly attacks healthy hair follicles.
• Manifestation: Begins with sudden, smooth, round or oval bald patches on the scalp.
• Advanced Variants:
  • Alopecia Totalis: Complete loss of all scalp hair.
  • Alopecia Universalis: Complete loss of all body and facial hair (eyebrows, eyelashes, body hair).

3. Postpartum Alopecia

• Cause: Temporary hair loss occurring at the conclusion of pregnancy. During pregnancy, elevated estrogen levels delay the telogen phase, keeping hair in anagen. After childbirth, hormone levels drop rapidly, shifting a large percentage of hairs into telogen simultaneously.
• Recovery: Full growth pattern typically returns within 9 to 12 months postpartum.

4. Telogen Effluvium

• Cause: Rapid shifting of hair follicles from the anagen phase into the telogen phase due to systemic shock, high fever, severe psychological stress, major surgery, general anesthesia, or crash dieting.
• Recovery: Reversible once the underlying stressor or health issue is resolved.

5. Traction Alopecia

• Cause: Physical, mechanical hair loss caused by continuous, excessive pulling or tension on the hair roots.
• Common Sources: Tight ponytails, heavy dreadlocks, tight braids, weaves, or improper extension application. Early intervention prevents permanent follicular scarring.

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Scalp Disorders & Clinical Recognition

Cosmetologists must carefully analyze the scalp prior to providing any service. Scalp disorders are categorized into non-contagious conditions (which can be treated with over-the-counter or salon treatments) and contagious infections (which mandate refusal of service).

Non-Contagious Scalp Conditions (Pityriasis / Dandruff)

Dandruff is scientifically termed pityriasis. It is characterized by excessive shedding and accumulation of skin cells. It is caused by an overgrowth of a naturally occurring micro-fungus called Malassezia.

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Contagious Infections & Mandatory Service Refusal

VIRGINIA BOARD REGULATORY REQUIREMENT: Under 18VAC41-20 regulations, cosmetologists are strictly prohibited from performing services on clients displaying signs of contagious disease, parasitic infestation, or open lesions. The cosmetologist MUST decline service tactfully, maintain proper sanitation, and advise the client to consult a licensed physician.

[ Contagious Scalp Infection Categories ]
  +--> Fungal (Tinea Capitis, Tinea Favosa)
  +--> Parasitic (Pediculosis Capitis, Scabies)
  +--> Bacterial (Folliculitis, Furuncles, Carbuncles)

1. Fungal Infections (Tinea / Ringworm)

• Tinea Capitis (Ringworm of the Scalp): Characterized by red papules or spots at follicle openings; hair breaks off easily, leaving dull, stubbly stumps and scaly red patches. Highly contagious via combs, brushes, and caps.
• Tinea Favosa (Favus): Characterized by dry, sulfur-yellow, cup-like crusts on the scalp called scatula. Has a distinct musty odor and can lead to permanent pink bald scars.

2. Parasitic Infestations

• Pediculosis Capitis (Head Lice): Infestation of the scalp with head lice parasites. Symptoms include intense itching and visible egg sacs (nits) cemented firmly to the hair shafts near the scalp. Transmitted by head-to-head contact or shared hats/towels.
• Scabies: Contagious skin disease caused by the itch mite (Sarcoptes scabiei), which burrows under the skin to lay eggs. Produces intense nighttime itching, red vesicles, and pustules on the scalp, body, or webbed skin between fingers.

3. Bacterial Staphylococci Infections

• Folliculitis: Infection of hair follicles causing small red pustules with a hair in the center, caused by Staphylococcus aureus.
• Furuncle (Boil): An acute, localized bacterial infection of a hair follicle producing constant, intense pain, swelling, and pus formation.
• Carbuncle: A severe bacterial inflammation of subcutaneous tissue caused by staphylococci; larger and deeper than a furuncle (a cluster of multiple boils).