Board-Certified Dermatologist Explains How to Fix Damaged Hair

Hair care might seem straightforward, but let’s be honest—most of us are winging it. Is my hair thin or just fine? Thick or high-density? Understanding hair texture helps you choose the right products and styling techniques so you can learn how to fix damaged hair.

Hair consists primarily of keratin protein, with a core called the cortex surrounded by a protective layer of cuticles. This outermost layer functions like shingles on a roof, sealing moisture in and shielding the hair. Over time, heat styling, chemical treatments, and even water exposure wear down these cuticles, leaving hair fragile and prone to breakage.

Hair Thickness vs. Hair Density

These two terms are often used interchangeably, but they’re completely different.

Hair Thickness

This refers to the diameter of a single hair strand. To figure out if your hair is thick or thin, pluck a strand and compare it to a piece of sewing thread. If your hair is as wide or wider, you have thick hair. If it’s noticeably finer, you have thin hair. Another trick? Run a strand through your fingers. Thick hair is easily felt, while thin hair is harder to detect.

Hair Density

Hair density describes how much hair you have overall. To check, pull your hair into a ponytail and measure the circumference:

Less than 2 inches: Low-density

Product Recommendation for Thin or Low-Density Hair: Volumizing foams and dry shampoos add body without making hair greasy.

More than 4 inches: High-density

Product Recommendation for Thick or High-Density Hair: Smoothing oils and hydration masks keep hair manageable and nourished.

If ponytails aren’t your thing, look in the mirror. Can you see your scalp without moving your hair? That’s a sign of low density. If your scalp is well-covered, you’re rocking high-density hair.

Understanding Curl Patterns

Nearly everyone has some degree of wave or curl. Understanding your curl pattern is key to choosing the right products and techniques.

Wavy Hair (Type 2)

• 2A: Slight waves that barely bend. Think “straight with a hint of texture.”
• 2B: More defined waves, with some areas showing an “S” pattern.
• 2C: Tight waves with more volume and texture. These waves often lean toward curls.

Product Recommendation: Lightweight sea salt sprays can enhance texture without weighing down the hair. Avoid heavy creams that flatten waves.

Curly Hair (Type 3)

• 3A: Loose curls that resemble a curling iron’s results—defined yet relaxed.
• 3B: Medium-sized spirals with bounce and body.
• 3C: Corkscrew curls that are densely packed and have significant shrinkage.

Product Recommendation: A good curl cream or gel can define curls without crunch. Look for moisturizing ingredients to combat frizz.

Coily Hair (Type 4)

• 4A: Tightly coiled hair with a soft texture.
• 4B: Zig-zag patterns with tighter, less uniform coils.
• 4C: The tightest coils with maximum shrinkage and volume.

Product Recommendation: Rich oils and butters are your best friends. They lock in moisture and help define your curl pattern.

Is Your Hair Damaged or Healthy?

People often misjudge the health of their hair. Let’s break it down:

Signs of Damaged Hair

• Tangling: If your hair tangles easily, it’s likely dry or damaged.
• Split ends: Visible splits at the ends of your strands are a clear indicator.
• Stretch test: Stretch a strand. If it elongates and snaps, it’s damaged. Healthy hair snaps immediately without stretching.
• Drying time: If your hair takes forever to dry and isn’t particularly dense, it could be damaged.
• Hair loss: Losing clumps of hair while brushing is a red flag for damage.

How to Fix Damaged Hair

If you’re dealing with damage, don’t despair—there are actionable steps you can take to repair and protect your hair.

Cleansing is a double-edged sword for damaged hair. While necessary to remove buildup of oils, sweat, and dirt from the scalp, over-shampooing can strip hair of its natural oils, exacerbating dryness. Dr. Jenny Liu, a board-certified dermatologist, advises focusing shampoo application on the scalp rather than the hair shaft to minimize damage. “Shampoos are meant to cleanse the scalp, not the hair itself,” she explains, emphasizing that detergents in shampoo can leave hair feeling brittle.

For those with dry or damaged hair, consider pre-treating your strands with coconut oil before shampooing. Coconut oil penetrates the cuticles, reducing hydro fatigue (the rapid swelling and contracting caused by water) and shielding hair fibers from further breakage. If oil feels too heavy, a leave-in conditioner can serve as an alternative pre-shampoo barrier.

Always follow shampooing with a conditioner to smooth the cuticles and restore manageability. For particularly dry or processed hair, incorporating a deep conditioning treatment weekly or monthly can provide an extra dose of moisture and temporary strength.

Heat and UV Protection

Heat styling and UV exposure are major contributors to damaged hair. “Ultraviolet radiation breaks down hair protein and color,” Dr. Liu warns. Before using heat tools, apply a protectant that guards against high temperatures and UV damage. Products like the Living Proof Heat Protectant Spray not only shield hair but also condition it lightly, making them dual-purpose solutions.

Additionally, limiting heat styling and opting for air drying when possible will reduce stress on your hair. If air drying isn’t an option, consider using a microfiber or specialized hair towel to wick away water quickly, cutting down on drying time and the need for heat tools.

Treatments for Serious Damage

When it comes to repairing severely damaged hair, deep treatments can make a significant difference. Dr. Liu highlights the benefits of two standout products: Olaplex No. 3 and K18. “Olaplex works by temporarily repairing disulfide bonds in the hair, while K18 goes deeper, using peptides to permanently fill gaps in the cortex and restore strength,” she explains.

For those struggling with compromised hair from bleaching or chemical treatments, these treatments can be transformative. However, Dr. Liu cautions, “Severely damaged hair can never be restored to its original state. In such cases, trimming is necessary.”

Understand Your Scalp Type Before Buying Hair Products

Your scalp is the foundation of healthy hair, and understanding its type can make or break your routine. Scalp types generally fall into three categories: oily, dry, and normal.

Oily Scalp

An oily scalp usually reveals itself by midday or evening, even if you washed your hair that morning. If your hair feels greasy, looks piecey, or your scalp shines by the end of the day, you’re likely dealing with excess oil production. This could be due to over-washing, hormonal imbalances, or just genetics. While this type may require frequent washing, avoid harsh shampoos that strip your scalp and exacerbate oil production.

What Hair Products to Use for Oily Scalp

Shampoos with silicone and heavy oils like coconut oil and shea butter can make your scalp even oilier. Instead, look for shampoos with exfoliating ingredients like lactic, citric, or salicylic acid, as well as tea tree or green tea extracts, which are great for oil control and soothing—because an oily scalp that doesn’t get cleansed properly can feel itchy.

If your shampoo doesn’t have exfoliating ingredients, look for salicylic acid or BHA drops to exfoliate your scalp once a week. There are also plenty of leave in conditioners and serums for oily scalps that contain exfoliants and prevent sebum production.

If itchiness is a big concern for your oily scalp, using shampoos with deep cleansing agents like sulfates and sulphonates can help. If itchiness is a direct result of dandruff, you’ll need anti-dandruff shampoos with ingredients like ketoconazole and zinc pyrithione to clear your scalp.

Even oily scalps need some hydration—glycerin, aloe vera and hyaluronic acid are all great ingredients to hydrate your scalp without weighing down your hair.

Dry Scalp

Think of a dry scalp like the Sahara Desert. It’s often itchy, tight, and prone to irritation. Flakiness can occur, but it’s not always dandruff—it could be due to a lack of moisture. A gentle, hydrating shampoo and scalp oil can work wonders for this type. Dry scalps can also benefit from more infrequent washes—think once a week or every 5-6 days depending on how dry your scalp gets.

What Hair Products to Use for Dry Scalp

Just like with oily scalp, ingredients like sulfates and fragrance can exacerbate the problem. Use gentle shampoos without any harsh exfoliants that may strip your scalp of moisture, making it even more dry and irritated. Remember all the heavy oils like coconut oil and shea butter we wanted to avoid for oily scalp? For dry scalp, we want a shampoo with these moisturizing ingredients.

Your dry scalp could also use some pre-wash TLC; massage a few drops of the Moroccan Oil Dry Scalp treatment into your scalp. Post-shower treatment is equally important. A hydrating serum

Why Understanding Your Hair Matters

Knowing your hair and scalp type and the scale of damage is the first step in building a routine that works for you. Ultimately, the key to managing damaged hair lies in consistent care. Focus on gentle shampooing, regular conditioning, and protecting your hair from heat and UV exposure. Incorporate treatments like K18 for deeper repair, and don’t hesitate to trim damaged ends when needed. As Dr. Liu puts it, “Healthy hair starts with how you care for it daily.”