Hair growth is a complex biological process. When hair appears to stop growing or thins unexpectedly, it is a concern. Many factors, from internal bodily functions to external care practices, influence hair growth. Understanding these influences helps address concerns.
The Hair Growth Cycle
Hair growth follows a cyclical pattern, with each strand undergoing phases. The longest phase is the anagen, or growth phase, where cells in the hair root rapidly divide, leading to hair lengthening. For scalp hair, this phase typically lasts between 2 to 8 years, with hair growing about half an inch per month. 85% to 90% of scalp hairs are in this active growth state at any given time.
Following the anagen phase is the catagen, or transitional phase, lasting about 10 days to a few weeks. During this period, hair growth slows, and the follicle shrinks and detaches from its blood supply. The hair shaft separates, forming a “club hair” that remains anchored until it’s shed.
The telogen, or resting phase, typically spans about 2 to 3 months. Hair does not grow during this phase, but it usually remains in the follicle. 10% to 15% of scalp hairs are in the telogen phase at any given moment. This phase concludes with the exogen, or shedding phase, where old hairs are released, often aided by washing or brushing, as new hairs begin to form in the same follicles. Losing 50 to 100 hairs daily during this phase is considered normal.
Underlying Factors Affecting Hair Growth
Various internal and external elements can disrupt the hair growth cycle, leading to slowed growth or increased shedding.
Nutritional deficiencies often disrupt hair growth, as follicles require vitamins and minerals. A lack of protein, the primary component of hair (keratin), can result in weak, brittle hair and impaired growth. Iron deficiencies can reduce oxygen transport to hair follicles, causing hair to shed faster than it grows.
Biotin (Vitamin B7) supports hair health; deficiency can lead to brittle hair and hair loss. Zinc supports cell division, tissue repair, and hormone regulation, influencing hair growth; low levels can cause thinning and slow growth. Inadequate Vitamin D levels have been linked to hair loss and thinning.
Hormonal imbalances can impact hair growth patterns. Thyroid disorders can disrupt the hair cycle, leading to diffuse hair loss. Polycystic Ovary Syndrome (PCOS) can contribute to hair thinning due to excess androgens. These hormonal fluctuations can shorten the anagen phase, preventing hair from reaching full length.
Medical conditions and medications can influence hair growth. Autoimmune conditions, such as alopecia areata, where the immune system attacks hair follicles, can cause hair loss. Major illnesses or physiological stress can trigger telogen effluvium, where a large number of hairs prematurely enter the resting phase, leading to noticeable shedding a few months later. Many medications, including antidepressants, blood thinners, oral retinoids, and chemotherapy drugs, can interfere with the hair growth cycle, causing hair loss, though often temporary.
Chronic stress can affect hair health. Prolonged stress can push follicles into an early resting phase, leading to increased shedding. Poor sleep quality can disrupt the body’s natural rhythms, potentially affecting the hair cycle.
Hair care practices play a role in maintaining hair length and integrity. Excessive heat styling, harsh chemical treatments like perms or relaxers, and tight hairstyles that pull on hair can cause breakage and damage to the hair shaft and follicle, leading to hair loss. Aggressive brushing can physically damage hair, causing it to break rather than grow.
Genetics and age determine hair growth. Individual growth rates, hair density, and the likelihood of pattern baldness are influenced by inherited genes. As people age, the hair growth cycle changes; the anagen phase may shorten, and hair tends to become thinner and grow more slowly.
Strategies for Optimizing Hair Growth
Adopting a balanced diet supports healthy hair growth. Adequate protein intake, found in lean meats, eggs, and legumes, provides the building blocks for hair. Foods rich in iron, such as spinach and red meat, help ensure oxygen delivery to hair follicles. Sources of biotin (eggs, nuts) and zinc (oysters, seeds) can help prevent deficiencies that impair hair health. Omega-3 fatty acids, found in fatty fish, contribute to scalp health.
Gentle hair care practices minimize breakage and promote length retention. This includes using mild shampoos and conditioners, avoiding excessive heat styling, and limiting harsh chemical treatments. Opting for loose hairstyles over tight braids or ponytails can prevent traction on follicles. Detangling hair gently with a wide-tooth comb, especially when wet, can reduce physical damage.
Managing stress levels can positively impact hair health, particularly in cases of stress-induced shedding. Techniques such as mindfulness, yoga, regular exercise, and sufficient sleep can help mitigate the physiological effects of stress on the body and hair. Prioritizing mental well-being contributes to overall bodily functions, including a healthy hair cycle.
When hair growth concerns persist despite lifestyle adjustments, seeking professional help is advisable. A doctor or dermatologist can assess underlying medical conditions, such as hormonal imbalances or nutritional deficiencies, through blood tests. They can diagnose specific types of hair loss and recommend targeted treatments, which may include prescription medications or other therapies. Consulting a professional ensures an accurate diagnosis and a personalized approach to optimizing hair growth.