There are many different types of hair, including straight, curly, wavy, and coily. Depending on a person’s hair type, they may need to follow different care instructions, including what type of shampoo to use and how often to wash or cut it.

This article will provide some general information about hair types and detail some specific care instructions.

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Infographic by Diego Sabogal

Hair type typically refers to the shape of a person’s hair. Hair can be straight, wavy, curly, or coily.

According to one 2020 article, hair consists of two structures: the strand of hair itself, or the hair shaft, and the hair follicle.

The hair shaft consists of different layers, including the cortex, the surrounding cells, and, in thicker hair, a central medulla.

A 2017 study notes that the shape of the hair follicle determines the shape of a person’s hair. For example, the hair follicles for curly hair are in the shape of an S.

Genetic factors play a role in deciding the shape of a person’s hair follicle.

Learn more about what determines hair shape here.

Hair shape refers to the degree of curliness of a person’s hair.

One review article notes that different researchers have used different hair shape categorization systems in their research about hair. For example, some have used use labels such as:

  • stick straight
  • straight
  • wavy
  • big curls
  • small curls

Some hairstylists like to distinguish hair shapes into four categories. However, scientists do not use this categorization system in medicine or scientific research.

Hairstylists use the following categorization system:

Hair typeShape
Type 1: Straight• 1a: Very straight, fine or thin texture
• 1b: Straight with some bends
• 1c: Straight with a coarser texture
Type 2: Wavy• 2a: Wavy and fine
• 2b: Wavy with a slightly more defined S-shape
• 2c: Wavy with well-defined S-shaped waves
Type 3: Curly• 3a: Loose curls
• 3b: Tight and springy curls
• 3c: An S or Z shape that springs back into shape when stretched
Type 4: Coily• 4a: Loose coils
• 4b: Zig-zagging coils
• 4c: Tight coils


Hair density refers to the number of hairs that a person has on their head. The more hairs a person has, the higher that person’s hair density.

Hair structure

Hair structure refers to the thickness of the strands of hair. A person’s hair can be:

  • fine
  • medium
  • coarse

According to the World Trichology Society (WTS), hair thickness varies depending on the person. Some people have finer hairs than others. The WTS also notes that the hair fibers become shorter and finer as a person ages.


Hair porosity is a measure of the amount of moisture that a person’s hair can absorb.

Hair porosity depends on how many gaps or tears are present in the cuticle layer. The cuticle is the outer layer of the hair, which protects it from wear and tear.

According to one 2015 article, hair is naturally porous. However, hair that has sustained damaged due to bleaching or chemical treatments is more porous than untreated hair.

People may find it helpful to avoid strong chemical and high heat treatments to let their hair recover.

According to the American Academy of Dermatology (AAD), people can try the following when caring for their hair:

  • Shampoo: Wash the hair with shampoo as often as needed. This will typically be when the hair becomes oily, which can happen at different rates for different people. Those with oily skin and hair may need to shampoo more often. Concentrate the shampoo on the scalp.
  • Condition: A person should use a conditioner after each shampoo. Concentrate the conditioner on the tips of the hair.
  • Dry: People can either wrap their hair in a towel and let it air dry or use a blow-dryer on the lowest setting. Using a blow-dryer can cause more damage to the hair than natural drying. However, there is research to suggest that using a blow-dryer at a distance of 15 centimeters and moving it continually can cause less damage to the hair than air drying.
  • Brush: Brush the hair when it is damp using a wide-toothed comb.

People should select their shampoo and conditioner based on their hair type.

If possible, they should try to limit:

  • Weaves and hair extensions: If possible, wear weaves and extensions that are lightweight. Wearing hair that is tightly pulled back can lead to hair loss, or traction alopecia.
  • Chemically treating the hair: People should try to leave some between color touchups. In addition, they should try to have one treatment at a time. This is because very treated hair is more prone to breakage.
  • Drying the hair using a towel: This can pull or twist the hair, causing it to snap. It can also ruffle the hair cuticles.

There is some evidence to suggest that straight hair carries sebum more easily than curly hair. Sebum is a waxy, oily substance that a person’s skin produces. This means that people with straight hair may be more likely to get oily hair than those with curlier hair.

For this reason, people with straighter hair may wish to avoid the excessive use of certain hair products. These include:

  • any hair product that is labeled for dry hair
  • oils, such as olive, coconut, and jojoba oil
  • oil-based styling products
  • leave-on products

People with straight hair may also wish to wash their hair more frequently.

According to a 2015 article, a person with straight hair may need to use a more gentle approach to caring for their hair. This may involve:

  • using gentle shampoos
  • gently drying the hair with a towel
  • brushing or combing the hair gently

Over-brushing can damage curl definition. Therefore, people with curly hair may need to experiment to find the right amount of brushing for their hair.

Some other care tips for curly hair include:

  • reducing shampoo usage
  • air drying or using a diffuser on a blow-dryer
  • avoiding dense combs and brushes
  • avoiding heat styling tools

Some people may also wish to use hair mousses and gels that are intended for curly hair to maintain curl definition.

The AAD suggests the following tips for Black hair:

  • washing the hair no more than once per week
  • using conditioner at every wash
  • avoiding overly tight braids, cornrows, or weaves
  • using a hot oil treatment fortnightly
  • using heat protecting products before heat styling

Additionally, people may wish to take care when using weaves or extensions. To prevent hair damage, they may wish to try:

  • ensuring that their hair is clean and free from hair products, including hair spray, before getting a weave or extension
  • using conditioner to help keep the hair strong
  • visiting a professional hairstylist, if possible
  • using a gentle shampoo to keep the scalp clean
  • protecting the hair’s edges using moisturizers and water-based gels

Tight hairstyles can also lead to traction alopecia, which results in hair loss. People may wish to consider giving the hair a break after 2–3 months of wearing a weave or extension.

Learn more about Black hair care tips here.

People with thick hair may find it helpful to use denser hair products, such as:

  • hair gels
  • hair butters
  • hair masks, such as avocado hair masks
  • thicker oils, such as coconut oil

Additionally, people with greater hair density may find it beneficial to use brushes that are designed for thick hair. These brushes have fewer spokes than others, which helps people remove knots without breaking the hairs.

There is anecdotal evidence to suggest that denser hair products, such as oils and butters, can weigh down thinner hair. For this reason, people with thin hair may wish to avoid these products.

People with thinner hairs may also benefit from:

  • using dry shampoo
  • washing the hair regularly
  • only applying conditioner to the ends of the hair

The WTS notes that people shed approximately 50–150 hairs per day. This can occur through hair washing, brushing, and combing. However, some people lose more hair than they can grow.

This can happen for various reasons. One common cause is androgenetic alopecia. This is a genetically predetermined condition that affects around 50% of people. In males, hair loss occurs at the temples and the top of the head. In females, hair loss can affect the crown.

Hair loss can also occur in females due to other health conditions, including:

  • polycystic ovary syndrome
  • a side effect of medication, such as birth control
  • thyroid problems

A person should contact a doctor if they:

  • experience sudden hair loss
  • develop bald patches
  • lose clumps of hair
  • experience itching and burning sensations on the scalp

Is it preventable?

Some anecdotal evidence suggests that people can use certain shampoos, essential oils, and dietary supplements to thicken the hair. However, there is no scientific evidence to prove that hair care can prevent thinning hair.

That said, a person can take measures to help prevent some causes of hair loss, such as traction alopecia.

Learn more about stopping hair loss here.

Everyone’s hair is slightly different. A person’s hair can be straight, curly, coily, or wavy, and each type benefits from different methods of care.

Although some hair loss is common, a person should contact a healthcare professional if they are concerned.