Can Your Hair Type Change? The Science and Surprising Reasons Why

Contents:

• Your Hair Type Isn’t Fixed—It Can Change
• The Science Behind Hair Type Changes
• Common Causes of Hair Type Change
• Hormonal Fluctuations
• Puberty and Adolescence
• Chemical Treatments and Damage
• Climate and Environmental Factors
• Health Status and Nutritional Deficiencies
• What the Pros Know: The Seasonal Hair Timeline
• Hair Type Change vs. Hair Condition: What’s the Difference?
• Adapting Your Routine When Your Hair Texture Shifts
• FAQ
• Can your hair type permanently change?
• Does pregnancy change your hair type permanently?
• Can you have two different hair types on your head?
• Why is my hair texture different than my parents’?
• How do I know if my hair type changed or if it’s just in bad condition?

Your Hair Type Isn’t Fixed—It Can Change

You’ve probably heard that your hair type is determined at birth and never changes. That’s actually a misconception. While your hair’s genetic blueprint doesn’t shift, your hair type absolutely can change due to hormonal fluctuations, environmental factors, ageing, chemical treatments, and health changes. Many people reach adulthood with straight hair, only to develop waves or curls in their thirties. Others find their once-coily hair loosens as they age. These changes are real, common, and entirely normal.

Understanding whether and why your hair type might change helps you adapt your care routine for better results. Rather than fighting your hair’s current texture, you can work with it—and anticipate shifts before they happen.

The Science Behind Hair Type Changes

Hair type is determined by the shape of your hair follicle, which is genetically controlled. A straight follicle produces straight hair; a curved follicle produces waves or curls. But the expression of these genetics—how tightly coiled or straight your hair appears—fluctuates throughout your life based on hormones, health, and environment.

The primary culprit is hormonal change. During puberty, pregnancy, menopause, and even during certain medication cycles, hormonal shifts alter how your hair grows from the follicle. A 2023 study published in the Journal of Cosmetic Dermatology found that approximately 40% of women experience measurable changes to their hair texture within 5 years of major hormonal events like pregnancy or menopause.

Beyond hormones, your hair texture responds to moisture, climate, chemical treatments, and overall health. A person with fine, straight hair living in humid London might develop waves during summer months, then revert to straighter texture in drier winter conditions. This isn’t permanent change but rather environmental responsiveness—your hair’s natural behaviour adapting to its surroundings.

Common Causes of Hair Type Change

Hormonal Fluctuations

Pregnancy is the classic example. Many pregnant women report their hair becoming thicker, curlier, or completely transforming texture during the nine months of elevated oestrogen. Conversely, postpartum hormonal crashes can reverse these changes within months of delivering. Some women experience this transformation and love it so much they pursue chemical treatments to maintain the new texture.

Menopause presents another hormonal milestone. Declining oestrogen levels can make hair thinner, drier, and sometimes straighter—particularly if your hair previously had natural wave or curl. Thyroid conditions, PCOS (polycystic ovary syndrome), and hormonal contraceptives can similarly affect hair texture because they alter hormone levels.

Puberty and Adolescence

Children often have noticeably different hair than their teenage or adult selves. Fine, straight blonde hair might darken and develop waves during puberty. Alternatively, curly-haired children sometimes find their curls relax as they mature. This occurs because androgen levels (male and female sex hormones) shift during puberty, directly influencing hair follicle shape and protein structure.

Chemical Treatments and Damage

Permanent or semi-permanent hair dyes, relaxers, perms, and heat styling don’t change your hair’s genetic type, but they dramatically alter how your hair appears and behaves. A person with naturally curly hair who uses chemical relaxers regularly will have straighter-appearing hair for months. Once the relaxer grows out, their natural curl pattern returns. Similarly, repeated bleaching or keratin treatments change your hair’s structure temporarily.

Climate and Environmental Factors

Humidity, water hardness, and seasonal changes noticeably affect hair texture. Hard water—common in parts of the UK, particularly southern England—deposits minerals that coat your hair and alter how it behaves. Installing a water softener can sometimes reveal that your hair was never as straight or thick as you thought; the mineral buildup was masking your natural texture.

Seasonal shifts matter too. Many people find their hair texture changes between summer (humid, making waves more pronounced) and winter (dry, sometimes making curls tighter or relaxing waves). This isn’t permanent change but cyclical responsiveness.

Health Status and Nutritional Deficiencies

Severe stress, illness, or nutritional deficiencies affect hair growth and texture. Iron deficiency, vitamin D deficiency, and protein malnutrition can make hair thinner, drier, and more fragile. Once these health issues resolve, your hair often returns to its previous texture. A person recovering from illness or improving their diet might notice their hair becoming noticeably stronger and curlier (if they have natural curl) within 2–3 months.

What the Pros Know: The Seasonal Hair Timeline

Hair Type Change vs. Hair Condition: What’s the Difference?

A critical distinction: your actual hair type rarely changes, but your hair’s condition frequently does. Hair type refers to whether you have straight, wavy, curly, or coily hair. Hair condition refers to whether it’s dry, oily, damaged, or healthy.

Someone with naturally curly hair might experience a period where their curls appear limp and undefined due to moisture loss or product buildup. They might assume their hair type has changed to wavy or straight. Actually, their hair type remains curly; the condition has simply deteriorated. Once they restore moisture and remove buildup through proper care, their curl pattern springs back to its original form.

This distinction matters because the solutions differ. If your hair type has actually changed, you need to adjust your entire routine. If your condition has declined, targeted treatments (deep conditioning, clarifying, protein masks) restore your original texture within weeks.

Adapting Your Routine When Your Hair Texture Shifts

If you genuinely experience hair type change—whether hormonal, environmental, or age-related—resist the urge to panic. Instead, observe your new texture for 4–6 weeks before making major product changes. Your hair might simply be adjusting to a new climate or seasonal shift.

Once you’ve confirmed a genuine shift, gradually introduce products suited to your new texture rather than abandoning your current routine overnight. If you’re developing more waves or curls, invest in moisturising conditioners and curl-defining products (£8–£20 depending on brand). If your hair is becoming straighter or finer, switch to lightweight shampoos and volumising sprays (£5–£12).

Many UK salons offer texture consultations where stylists assess whether changes are genuine or condition-related. This costs £20–£40 and provides valuable clarity before you spend money on new products.

FAQ

Can your hair type permanently change?

Hair type can change temporarily due to hormones, climate, and treatments, but your genetic hair type remains constant. Chemical relaxers or perms create temporary changes; once they grow out, your original texture returns. Permanent shifts due to ageing or severe hormonal change do occur but are relatively rare.

Does pregnancy change your hair type permanently?

Pregnancy causes temporary hair texture changes due to elevated oestrogen. Most changes reverse within 6–12 months postpartum. Some women retain their new texture, but this is unusual. Plan for your hair to shift back toward its pre-pregnancy state within a year.

Can you have two different hair types on your head?

Absolutely. Many people have straight hair on top with curlier texture underneath, or waves in some sections and straight hair in others. This reflects varied curl patterns across different sections of your scalp—entirely normal and not indicative of change.

Why is my hair texture different than my parents’?

You inherit hair type genetics from both parents, but the combination can produce textures different from either parent. Additionally, hormonal, environmental, and health factors expressing differently in your life than in your parents’ means your hair might look and behave quite differently despite sharing similar genetics.

How do I know if my hair type changed or if it’s just in bad condition?

Condition changes happen quickly (weeks); type changes happen gradually (months). If your hair suddenly looks limp or frizzy, it’s likely condition-related. If you’ve noticed texture shifts over several months despite consistent care, it’s probably genuine type change. When in doubt, consult a salon professional.