Curly hair is caused by the shape of the hair follicle. Hair follicles are the pores from which each strand of hair grows. Straight hair grows from a round hair follicle. Curly or wavy hair grows from an oval-shaped hair follicle.
The Structure of Hair
Hair is made up of a protein called keratin that is produced in the hair follicles. Keratin contains long chains of amino acids that bind together to form a rigid structure. This structure gives hair its straightness or curliness.
There are three layers that make up each hair strand:
- Cuticle – This is the outermost layer made up of overlapping cells like shingles on a roof. This acts as a protective barrier for the inner layers.
- Cortex – This middle layer contains bundles of keratin and melanin that give hair its color and texture.
- Medulla – The soft, innermost layer that contains air spaces. This layer is absent in fine and curly hair.
What Makes Hair Curly?
The shape of the cortex determines whether hair is curly or straight. In straight hair, the cortical fibers are arranged parallel to each other. In curly or wavy hair, the fibers are arranged in an elliptical or oval shape.
As new keratin proteins are produced, they shift the hair follicle into an oval shape. This causes the hair strands growing out of the follicle to bend and curve, resulting in curls or waves.
The tighter the oval shape, the tighter the curls. The more elongated the oval, the looser the waves.
Factors That Influence Hair Curlyness
There are several factors that can determine how curly someone’s hair is:
Hair Texture
Texture refers to the thickness or diameter of each hair strand. Those with an oval-shaped follicle and fine, thin hair are more likely to have tighter coils. Thicker, coarse hair with the same follicle shape will have looser curls.
Race and Ethnicity
Genetics play a major role in curl pattern. Those of African descent tend to have oval-shaped follicles and tighter curls. Caucasians and Asians are more likely to have round follicles and straight hair.
However, curly hair can occur in people of all backgrounds. Many Mediterranean, Middle Eastern, Hispanic, and mixed race people also commonly have curly or wavy hair.
Age
Curly hair often becomes less defined as people age. Hair follicles shrink over time, resulting in straighter hair. Hormonal changes, especially declining estrogen in women, can also affect texture.
Kids with stick-straight hair can develop waves or curls around puberty when hormone production ramps up. Then hair may return to being straight after menopause when hormones stabilize.
Health and Medical Conditions
Certain medical conditions are associated with curly hair:
- Pregnancy – Surging hormones like estrogen can create looser curls or temporary straightening.
- Thyroid disorders – Both hypothyroidism and hyperthyroidism can increase curliness.
- Nutrient deficiencies – Lack of protein, vitamins, or minerals like iron, zinc may alter texture.
- Down syndrome – Most people with Down syndrome have curly hair.
Some medications and treatments can also affect curl pattern:
- Birth control pills
- Anti-fungal medications
- Immunosuppressant drugs
- Chemotherapy
- Radiation treatment
Talk to a doctor if new curls or texture changes occur with a new medication.
Making Curly Hair Straighter
While curly hair is beautiful in its natural state, some people with curlier locks desire straighter styles. There are a few temporary and permanent ways to straighten curls.
Temporary Straightening
These methods only straighten hair for a day or two before curls return. They do not affect the underlying hair structure.
- Blow drying – Using high heat and tension from a round brush can stretch out curls for a smoother look.
- Flat ironing – Ceramic flat irons apply high heat to relax the hair fibers and bonds.
- Chemical relaxers – Strong alkaline solutions like lye break down bonds temporarily. Lasts 2-3 months.
- Japanese hair straightening – A two-step process of applying protein filler and formaldehyde solution. Lasts up to 6 months.
These techniques must be repeated frequently to maintain straight styles. They can also damage hair if overused.
Permanent Straightening
Permanent options rearrange the hair structure for straight styles that last months to years.
- Keratin treatment – Keratin is infused into the hair and sealed in with a flat iron. Smooths hair for 2-4 months.
- Brazilian Blowout – A keratin solution is applied and locked in with heat tools. Lasts 3-4 months.
- Permanent relaxer – Severe alkalis like lye are applied to permanently rearrange bonds. New growth will be curly.
- Japanese thermal reconditioning – Hair is treated with chemicals, rolled on rods, and heated to rebond hair fibers.
These chemical processes can be damaging if not done properly. Seek professional services for perms and relaxers. Be aware that perfectly straight hair is unrealistic for most; a looser wave is the best outcome.
Caring for Curly Hair
Curly hair has different needs than straight hair. Here are some tips for maximizing the health and appearance of natural curls:
- Shampoo less often, 1-2 times per week.
- Use moisturizing shampoos and conditioners.
- Detangle gently with a wide-tooth comb when wet.
- Pat dry gently with a cotton t-shirt.
- Apply products like leave-in conditioner when wet.
- Let air dry or use diffuser attachment on blowdryer.
- Use microfiber towels.
- Avoid heat styling tools.
- Use soft scrunchies instead of hair ties.
- Trim regularly to remove split ends.
The right haircare regimen prevents dryness and frizz while enhancing natural curl definition. Seek help from a stylist who specializes in curly hair for cut and product recommendations.
Common Curly Hair Types
There are a wide variety of curl patterns and textures seen around the world. Here are some of the most common curl types:
Type 2 – Wavy
Type 2 hair falls into loose waves rather than ringlets. The oval shape of follicles is elongated. Normal to thick hair with this texture looks wavy. Fine hair may appear straight but frizzes easily.
Type 3 – Curly
Type 3 hair has well-defined, springy curls. Coils range from wide spirals to tight corkscrews. Shrinkage is moderate. This hair type is common among those of mixed ethnicity.
Type 4 – Coily
Type 4 hair has very tight curls that appear similar to coils or zigzags. The strands easily intertwine. Shrinkage of 75% or more is typical. This texture is most common in people of African descent.
Within these types there are further sub-classifications:
| Type | Sub-types |
|---|---|
| Type 1 | 1a – Straight 1b – Wavy |
| Type 2 | 2a – Loose waves 2b – Defined waves 2c – Tight waves |
| Type 3 | 3a – Wide curls 3b – Corkscrews 3c – Tight curls |
| Type 4 | 4a – Tight coils 4b – Z-shaped coils 4c – Coiled coils |
As you move from 1 to 4 and a to c, the curl pattern becomes progressively tighter and more defined. There are also various nuances within each subtype not explained by the code.
Embracing the Curl
Although popular culture has often promoted straight hair as the ideal, perceptions have shifted in recent decades. The natural hair movement encourages embracing curls and rejecting damaging straightening treatments.
There are more products, salons, and resources dedicated to curly hair care than ever before. Celebrities like Zendaya, Tracee Ellis Ross, and Yara Shahidi proudly show off their curls on the red carpet.
While curiosity about straightening still exists, a growing number of people with naturally curly hair have gained an appreciation for their unique locks. There are no “bad” or “unprofessional” hair types.
The healthiest approach is to work with your natural texture and find styling techniques that enhance your curls. Curly hair is versatile – it can be worn straight for occasions or amplified into full, bouncy curls.
Though it requires specialized care, curly hair is beautiful in its many forms.
Conclusion
Curly hair develops based on the shape of the hair follicles within the scalp. Oval or elliptical-shaped follicles produce bent hair shafts that lead to wavy, coily, or kinky hair.
Genetics play a huge role in determining curl pattern and are responsible for the variations seen amongst different ethnicities. Hair type can also be affected by age, hormones, health conditions, and medications.
While temporarily straightening is possible with certain tools and treatments, permanent straightening requires harsh chemicals that can damage the hair over time.
Embracing natural curls has become more popularized through the natural hair movement. With the right haircare regimen and styling techniques, curly hair is versatile and beautiful in its natural state.