Haircare 101: What Is Hair Made Of?

You don’t need us to tell you that hair can look and feel wildly different from person to person. But whether it’s pin-straight and oily or thick and dry, all hair is made of the same basic components. Understanding what hair is made of and how it’s structured can help you develop a haircare routine tailored to your unique needs, whether you’re addressing a specific concern or simply want to keep your strands in tip-top shape.

Ahead, we’ll break down the basic structure of hair and explain what it’s made of to help you better understand your strands. Then, we’ll share a few of our best haircare tips to support your hair from the inside out. Keep reading for your crash course on hair composition and structure.

What Is Human Hair Made Of?

According to the Cleveland Clinic, human hair consists primarily of keratin, a type of protein that’s also found in the nails and skin. Each strand also contains small amounts of natural lipids, water, minerals, and melanin—the latter of which is responsible for your natural hair color. The exact ratio of these compounds can affect how your hair looks, feels, and behaves.

What is keratin made of?

Nutrients in the foods we eat help our bodies produce keratin, and in turn, healthy-looking hair. There are several nutrients and micronutrients needed for healthy hair growth, but per Harvard Health, these are among the most important:

• Vitamin D: This essential vitamin, found in fatty fish, egg yolks, cheese, and fortified cereal, helps create the cells that develop into hair follicles. It’s also important for maintaining a healthy, functioning immune system.
• Iron: Iron helps your blood carry oxygen throughout your body and to your hair follicles. If you’re low in iron, your hair follicles may not get the oxygen they need to produce healthy, resilient hair.
• Vitamin C: Vitamin C, which is found in citrus fruits and leafy greens, helps your body absorb iron from your diet. It’s also a powerful antioxidant that can help protect your cells against oxidative damage.

Other nutrients that can help support healthy hair growth include vitamin B3 (niacin), vitamin B7 (biotin), and zinc. As Harvard Health notes, most people can obtain the necessary nutrients for strong, healthy hair by maintaining a well-balanced diet.

Hair Growth and Anatomy, Explained

Each strand of hair consists of two main structures: the follicle, which exists beneath the skin’s surface, and the shaft, which is the part that you see.

Hair follicles

The hair follicle, as mentioned, lies beneath the skin’s surface, typically extending into the dermal layer of your skin. Close to the surface, there’s a sebaceous gland, which produces oil to help lubricate your scalp and strands. At the base of the follicle is the hair bulb, the structure where your hair roots emerge and growth begins.

Hair grows as blood vessels deliver nutrients to the cells within the bulb, creating the root. As these cells multiply, older cells are pushed upward and out through the scalp, forming a visible strand of hair. This process occurs in three phases: anagen (active growth phase), telogen (rest phase), and catagen (transition phase). According to the Cleveland Clinic, the entire growth cycle can take up to seven years. However, you can typically expect to see roughly one centimeter of hair growth per month, or about six inches per year.

Hair shaft

The hair shaft refers to the visible strands that exist outside of your skin. The shape of the hair shaft and the angle at which it grows from the skin play a major role in determining your hair texture. The shaft is composed of two (or sometimes three) layers:

Cuticle layer: The cuticle is the outermost layer of your hair. It consists of dead, overlapping keratin fibers, as well as natural lipids that help protect your strands against external stressors, such as chemicals and heat.

Cortex layer: The cortex makes up the bulk of your hair. This thick inner layer plays an important role in determining how your hair looks and feels. The cortex is composed primarily of keratin linked together by hair bonds. These bonds play a crucial role in maintaining your hair's smoothness, strength, and healthy appearance.

Medulla layer: Those with thick hair may also have a medulla layer. If present, it’s the innermost layer of the hair and acts as a “core” of sorts.

What Affects Your Hair’s Characteristics?

Understanding your hair type is more than just labeling it as curly or straight—it’s about learning how your hair behaves so you can care for it in a way that works. Hair texture, porosity, and elasticity all play a role in how your strands respond to products, moisture, and styling. Getting familiar with these traits can help you build a routine that supports your hair’s health and makes styling easier and more effective.

Hair texture

Your hair texture is largely determined by the shape of your hair follicle. Round follicles produce straight hair, while oval or twisted follicles create wavy, curly, or coily textures. The more curved the follicle, the curlier the hair tends to be. These structural differences also affect how your hair retains moisture and responds to styling.

Straight hair tends to be smoother and can get oily more quickly, since sebum travels down the shaft more easily. Wavy and curly hair may struggle with frizz and uneven moisture distribution, while coily hair—often the most fragile type—typically needs richer, more hydrating formulas to maintain strength and definition. Knowing your curl pattern (or combination of patterns) can help you choose products and techniques that support your natural texture rather than fight against it.

Hair porosity and elasticity

Porosity refers to how well your hair absorbs and retains moisture, and it can be just as important as texture when it comes to choosing the right products. You can test your hair’s porosity by placing a clean strand in a glass of water—if it sinks quickly, your hair is likely highly porous; if it floats for a while, it’s likely low porosity. High-porosity hair absorbs moisture easily but can lose it just as fast. Low-porosity hair, on the other hand, resists moisture and may be prone to oiliness or buildup.

Elasticity, or how well your hair stretches and returns to its original shape, gives clues about its strength. Healthy, elastic hair is more resilient to breakage, while low elasticity hair is fragile and can often benefit from strengthening treatments. Bonding treatments, in particular, can be useful for those with fragile hair. We love the L’Oréal Paris EverPure Bond Repair line, which consists of a pre-shampoo treatment, a sulfate-free shampoo, a nourishing conditioner, and a smoothing leave-in hair oil. The four-piece system works in tandem to help reinforce fragile hair from the inside out for stronger, more resilient strands. Plus, it’s color-safe and suitable for all hair types.

How To Keep Your Hair Healthy-Looking

A healthy head of hair starts with the right habits. From cleansing your scalp to shielding your strands from daily wear and tear, every step of your routine plays a role in how your hair looks and feels. Ahead, we’re sharing some of our top haircare tips for strong, healthy-looking strands.

1. Prioritize scalp care

​​Healthy hair begins at the scalp. Just like your skin, your scalp can accumulate buildup from oil, sweat, and styling products, especially if you use styling aids every day. Regular scalp exfoliation can help remove this buildup, creating a cleaner environment for growth.

For gentle exfoliation that won’t leave your scalp feeling dry or stripped, we recommend the L’Oréal Paris Elvive Hyaluron + Pure Oil Erasing Serum. The gentle formula, which contains salicylic acid and hyaluronic acid, helps remove 100% of residue while hydrating your lengths for healthy-looking strands from root to tip.

2. Use products designed for your hair type and texture

One of the best tips for healthy hair is also the most obvious: Use products tailored to your hair type and texture. Dry hair has different needs than oily hair, and vice versa. Using products designed for your specific needs can help ensure your hair looks and feels its best day after day. If you need help determining which products to add to your routine, we recommend checking out our article How To Find the Best Shampoo for Your Hair (don’t worry—it includes conditioner recommendations, too).

3. Limit heat styling and chemical processing

Indulging in a weekly blowout and coloring your hair can be fun, but these habits can also take a toll on your strands over time. To help keep your hair looking and feeling its best, it’s a good idea to limit how often you bleach, dye, or heat style your hair. If you must color your hair, be sure to supplement your routine with reparative products designed to help hydrate and strengthen your strands, and opt for ammonia-free or semi-permanent colors when you can. And if you’re heat-styling your hair, be sure to prep your mane with a heat protectant first to help shield against unnecessary damage. If you need a recommendation, we love the L’Oréal Paris EverPure Sulfate-Free Moisture 21-in-1 Leave-in-Conditioner, which helps protect against temperatures up to 450 degrees Fahrenheit.

4. Detangle gently

Brushing and detangling your hair gently is one of the simplest ways to prevent breakage and preserve your strands’ health. Hair is especially fragile when wet, so it’s best to use a wide-tooth comb or a detangling brush designed to glide through knots without pulling or snapping the hair. Start from the ends and slowly work your way up to the roots, using short, gentle strokes to ease out tangles. If your hair is particularly prone to knots, applying a leave-in conditioner or detangling spray beforehand can add slip and reduce friction.

Signs Your Hair Might Need Extra Care

If you’re hoping to learn how to maintain healthy hair, one of the most effective skills you can learn is how to spot damage early. Below, we’re sharing a few common signs that your hair may be in need of some TLC so you can get to the root of the problem (pun intended) before it spirals out of control.

1. Dullness

Hair dullness is often a clear sign that your strands may be unhealthy or in need of extra care. When hair loses its natural shine and appears flat or lifeless, it typically indicates that the cuticle—the outer protective layer—is damaged in some way. To help prevent further damage, it’s a good idea to cut back on heat styling and opt for protective styles when you can. In the meantime, you can help boost shine with a glossing system. Try the L’Oréal Paris EverPure Glossing Shampoo and coordinating L’Oréal Paris EverPure Glossing Conditioner. The glycolic acid-infused duo helps seal the hair fiber, leaving your strands soft, smooth, and full of shine. Complete your routine with the L’Oréal Paris EverPure Sulfate-Free Glossing 5-Min Lamination Hair Mask for smooth, silky-looking strands.

2. Breakage and split ends

Split ends are a common sign of hair damage, occurring when the protective outer layer of the hair strand wears down and the fiber begins to fray or split. If left untreated, split ends can travel up the hair shaft, causing further breakage and weakening the overall health of your hair. Regular trims—typically every six to eight weeks—are the best way to prevent split ends from spreading and to keep your hair looking smooth and healthy.

3. Dryness

Hair dryness often signals that your strands are lacking the moisture and oils they need to stay healthy and resilient. When hair becomes dry, the protective cuticle can become rough or raised, allowing essential moisture to escape. This dryness can result from factors such as excessive heat styling, harsh chemical treatments, overwashing, or environmental stressors, including sun exposure and cold weather. To help lock in moisture and keep your strands hydrated, try adding a hair mask to your routine once or twice per week. We love the L’Oréal Paris Elvive Total Repair 5 Multi-Use Leave-In Treatment, which melts into the hair fiber and helps fortify your strands against damage. The L’Oréal Paris Elvive Total Repair 5 Damage-Erasing Balm is another excellent pick. It’s infused with a 17% repair concentrate with protein and deeply conditions to nourish dry, brittle hair.

Next Up: How To Strengthen Weak, Brittle Hair

Photo courtesy of L’Oréal Paris