Hair texture is defined by the shape and pattern of a hair strand, ranging from straight and wavy to curly and coily. Hair texture can shift throughout a person’s lifetime, sometimes subtly and other times quite dramatically. These alterations are rooted in biological and external factors that affect how the hair grows and is structured.
The Biology Behind Hair Texture
The texture of a hair strand is determined by the shape of its follicle. A perfectly round follicle produces straight hair, while an oval or flat-shaped follicle causes the hair shaft to bend, resulting in wavy or curly hair. The flatter the follicle’s shape, the curlier the resulting hair pattern will be.
Hair is primarily composed of keratin protein, and its structure is held together by chemical bonds. Disulfide bonds are the most stable, forming strong molecular links that dictate the hair’s permanent shape. Curler hair typically has more of these bonds, which are unevenly distributed along the shaft.
Weaker hydrogen bonds are also present, but they are temporarily broken by water or heat. This explains why hair temporarily loses its curl in high humidity or can be restyled with a flat iron, only to revert when wet. A change in texture means the follicle’s shape has been altered or the internal structure of the hair shaft has been permanently disrupted.
Internal Triggers: Hormonal and Age-Related Shifts
Fluctuations in the endocrine system, particularly sex hormones, directly influence the shape and function of the hair follicle. During puberty, a surge in hormones can cause a straight hair follicle to shift into a more oval shape, resulting in the development of waves or curls.
Pregnancy is a major hormonal event where high estrogen levels prolong the hair’s growth phase, often making hair feel thicker. The subsequent drop in estrogen after childbirth can trigger temporary postpartum hair loss. This hormonal reset may also result in a texture change, sometimes leading to increased dryness or frizz in the new growth.
Menopause involves a decrease in estrogen and progesterone, allowing androgens to have a greater influence. This shift can cause hair follicles to shrink, reducing hair density and volume. New hair may feel coarser, drier, or more wiry due to decreased sebum production within the aging follicle.
Age-Related Changes
Aging also contributes to texture alteration independent of hormonal shifts. As the body ages, the hair follicle can change, and the hair shaft may become finer. Gray hair, which lacks pigment, often results in a different texture; these strands frequently have a larger diameter and can feel rougher than pigmented hair.
Health and Stress
Health conditions that stress the body can impact hair growth and texture. Thyroid disorders, which affect keratin production, can make hair dry and brittle. Severe illness or physiological stress, such as a high fever, can temporarily push many hairs into the resting phase, manifesting as a texture change when the new hair emerges.
External Factors and Environmental Influence
Chemical processing uses strong agents to break and reform the hair’s internal disulfide bonds, resulting in a dramatic and permanent texture change. Procedures like perms, relaxers, and permanent hair dyes penetrate the hair shaft to fundamentally alter its structure or color.
This alteration inherently weakens the hair structure, often leading to increased porosity and protein loss. The protective outer layer (cuticle) can become damaged and lifted, causing the hair to lose moisture rapidly and feel rough or brittle. This change is permanent until the treated hair is cut off.
Heat and mechanical damage from styling tools also degrade texture over time. Excessive heat, typically above 300°F (150°C), evaporates internal moisture and denatures keratin proteins. This causes the protective cuticle to crack, leading to a loss of elasticity, frizz, and a collapse of the natural curl or wave pattern.
External factors like severe malnutrition or rapid climate changes affect the quality of new hair growth. A lack of protein, vitamins, or fatty acids results in weak and brittle hair. Moving from a humid to a very dry climate can strip the hair of moisture, making the texture feel significantly drier and rougher.
Reversing or Managing Texture Changes
When texture change is due to external factors like heat or chemical damage, the focus shifts to restoring hair integrity. Deep conditioning masks and protein treatments can replenish lost moisture and strengthen the compromised shaft. Minimizing high-heat styling and chemical treatments prevents further damage, allowing healthier hair to grow in.
For changes stemming from internal, biological shifts like aging or hormonal fluctuations, the change is usually permanent, requiring management rather than reversal. Since decreased oil production often accompanies these changes, adopting a regimen focused on intense hydration and moisture retention is beneficial. This includes using moisturizing shampoos and leave-in conditioners to address dryness.
Adapting to a new texture may require learning new styling techniques or using products formulated for the hair’s current density or curl pattern. If a sudden or severe texture change is suspected to be related to a medical condition or hormonal imbalance, consult a dermatologist or endocrinologist. These professionals can investigate underlying physiological causes and recommend targeted treatments.