Hair Oil vs Hair Serum: Which One Does Your Hair Actually Need

Hair oil nourishes and hydrates from within while hair serum coats the strands to smooth, protect, and fight frizz. While you don’t need both, using the right one can transform your hair care routine.

If you’re still wondering why your frizz won’t quit even after switching shampoos? It’s probably not your wash, it’s your leave-in.

In this guide, we’ll break down the real difference between hair oil and serum, when to use each, who it suits best, and how to layer them (if at all).

Hair Oil vs Hair Serum: Quick Comparison

Feature	Hair Oil	Hair Serum	Best For
Main Function	Deep nourishment, hydration	Frizz control, heat protection	Different hair needs
Texture	Rich, oily	Lightweight, slippery or silky	Preference-based
Where It Works	Penetrates hair shaft	Coats hair surface	Internal vs. external care
When to Use	On damp or dry hair, before/after styling	On damp hair before styling, or dry ends	Depends on styling habits
Concerns It Solves	Dryness, split ends, damage	Frizz, dullness, heat styling damage	Hair condition-specific
Hair Type Match	Coarse, dry, chemically treated	Fine to medium, frizzy, colour-treated	Hair texture-dependent
Layering	Can be used after serum (sparingly)	Often used before oil or as solo styling aid	Strategic layering works best

What Hair Oils Do Best

Hair oils go deep, quite literally.

They penetrate the hair shaft to replenish lost moisture, restore elasticity, and seal in nutrients. Think of them as daily vitamins for your strands, especially in Singapore’s hot, humid, and air-conditioned environment.

When to Use Hair Oil

You should use hair oil when your hair feels brittle, rough, or dehydrated. It’s also helpful after heat styling or colouring, as it repairs internal damage over time.

Best For:

• Thick, coarse, or dry hair
• Chemically treated or coloured hair
• Taming split ends and dryness

Common Oils in Haircare:

• Argan oil: Lightweight but deeply nourishing
• Coconut oil: Rich and ideal for deep conditioning
• Jojoba oil: Balances oil production on the scalp
• Camellia or grapeseed oil: Great for frizz without heaviness

Use Case:

If your ends feel dry every time you leave the house or your curls go frizzy by lunch, applying a few drops of oil to damp hair can lock in hydration and reduce breakage.

Start with 1–2 drops and warm it between your palms. Focus only on the mid-lengths to ends to avoid limp or greasy roots.

What Hair Serums Do Best

Unlike hair oils that seep in, serums coat each strand with a protective layer. They’re designed for instant payoff: smoother texture, shinier finish, and better protection against daily aggressors like styling tools or wet hot humid air.

When to Use Hair Serum

Use a serum when your hair is frizzy, flyaway-prone, or in need of extra shine. Apply before heat styling or on dry ends to refresh your look.

Best For:

• Fine to medium hair
• Frizz control in humid climates (like Singapore)
• Pre-styling protection for hair straighteners or hair dryer

Common Serum Types

• Frizz control serums: Typically silicone-based, lightweight, and ideal for smoothing
• Moisture or plumping serums: Often include hyaluronic acid or panthenol for hydration
• Bond-repair or strengthening serums: Help reinforce damaged strands

Real-Life Use Case

Imagine you’re about to head outside the scorching sun after a blowout, but thankfully the serum acts like a shield, retaining your fabulous hair. A few drops worked through the ends can prevent puffiness and dullness for hours.

Always apply serums to damp hair (not soaking wet) before styling, or smooth a light amount over dry hair as a touch-up.

Using Both Hair Oil and Hair Serum Together

In Singapore’s humid, hair-flattening weather, one product often isn’t enough. But that doesn’t mean you need to pile everything on. Used the right way, hair oil and serum can work together, kinda like kaya and toast, each bringing something important to the table.

When Layering Actually Helps

If your hair is always frizzy by lunchtime or loses shine the moment you step out of the air-con, this duo can save your strands. Here's how:

• Serum first: Acts like a humidity shield and frizz fighter
• Oil second: Locks in hydration and smooths down cuticles
• Perfect for: Dry, damaged, colour-treated, or frequently styled hair

When to Avoid the Double Act

This combo isn’t for everyone, especially if your hair leans on the fine or oily side.

• You have thin hair that gets greasy fast
• You already use rich masks, creams, or leave-ins
• You’re using heavier formulations not meant for layering

Your Easy, Layering Routine

After Shower
Pat dry your hair, then apply serum to damp strands, focusing on frizz-prone areas.

Before Blow-Dry / Air-Dry
Work in a few drops of hair oil from mid-lengths to ends to seal in moisture.

Post-Styling Touch-Up (Optional) If your ends still feel dry or flyaways appear, smooth a tiny bit of oil to finish.

Remember, Less is more, so start small and think pea-sized amounts. Build up only if your hair needs more love.

Hair Oil vs Hair Serum: What’s Best for Your Hair Type?

Hair Type / Goal	Use Hair Oil?	Use Hair Serum?	Best For
Fine or Flat Hair	Not recommended (use sparingly)	Yes	Lightweight smoothing and frizz control without heaviness
Thick or Coarse Hair	Yes	Yes	Deep moisture + surface polish for manageability
Curly or Wavy Hair	Yes	Yes	Frizz control and curl definition with hydration
Chemically Treated / Coloured Hair	Yes	Yes	Protection + repair for damaged, porous strands
Oily Scalp, Dry Ends	Yes (on ends only)	Yes	Targeted moisture + heat shield without greasing roots
Daily Styling / Heat Use	Yes (post-style)	Yes (pre-style)	Heat protection + post-styling shine and split-end sealing
Minimal Routine / Low Maintenance	✅ or ✅ (hybrid)	✅ or ✅ (hybrid)	One-product styling via oil-in-serum or serum-in-oil blends

Top Secret Recommended Hair Serum and Hair Oil Products

Product	Type	Best For	Key Features	Texture	Price (SGD)
Olaplex No.7 Bonding Oil	Hair Oil	Damaged, colour-treated, frizzy hair	Bond repair, heat protection, non-greasy shine	Lightweight oil	$33.80
Moroccanoil Treatment Original	Hair Oil	Dry, thick, or coarse hair	Argan oil-based, detangles, boosts manageability	Rich oil	$37.50
Kérastase Chronologiste Huile De Parfum	Hair Oil	Dull or ageing hair	Adds fragrance, shine and softness	Silky oil	$72.00
Goldwell Dualsenses Scalp Specialist Serum	Hair Serum	Thinning or shedding hair	Anti-hair loss care, lightweight scalp formula	Watery serum	$64.00
Olaplex No.9 Bond Protector Serum	Hair Serum	Heat-styled or pollution-exposed hair	Antioxidant-rich, anti-frizz, heat protection	Gel-like serum	$33.80
Kérastase Genesis Hair-Fall Fortifying Serum	Hair Serum	Weak hair prone to breakage	Strengthens roots, daily-use intensive care	Lightweight serum	$68.00

1. Olaplex No.7 Bonding Oil

A bond-repairing hair oil that boosts shine and shields from heat damage.

This cult-favourite oil is more than just a shine booster. It's formulated with the patented Olaplex Bond Building Technology™ to strengthen fragile strands while offering UV and heat protection up to 230°C.

Ideal For: Colour-treated, chemically damaged, or frizzy hair
Price: $33.80
Key Features:

• Bond repair and strengthening
• Non-greasy formula
• Heat and UV protection

“It’s a must-have if you style often or bleach your hair.” Darren Wong, Olaplex enthusiast 

2. Moroccanoil Treatment Original

A rich, argan oil-based formula that smooths, hydrates, and tames unruly strands.

Known for its signature scent and smoothing power, this oil softens thick or dry hair instantly. It also works as a pre-styling product or leave-in for extra moisture and frizz control.

Ideal For: Thick, coarse, or dry hair
Price: From $37.50
Key Features:

• Infused with antioxidant-rich argan oil
• Improves texture and manageability
• Adds long-lasting shine

3. Kérastase Chronologiste Huile De Parfum Hair Oil

A luxury oil that adds fragrance and radiance to ageing or dull hair.

This hair perfume oil delivers more than just scent, it deeply nourishes while protecting hair from dryness and oxidation. Think of it as skincare for your hair.

Ideal For: Ageing, tired, or dull hair
Price: $72.00 (was $90)
Key Features:

• Adds perfume-like scent to hair
• Restores suppleness and shine
• Smooth, non-sticky texture

“A pampering treat for days when you need to feel extra polished.”

4. Goldwell Dualsenses Scalp Specialist Anti-Hair Loss Serum

A targeted scalp serum that strengthens roots and slows shedding.

Formulated for fragile scalps, this weightless serum reduces hair fall by fortifying roots and soothing irritation. It’s ideal for postpartum shedding, stress-induced loss, or general thinning.

Ideal For: Hair loss, scalp care, or postpartum hair issues
 Price: $64.00
 Key Features:

• Boosts root strength
• Lightweight and non-greasy
• Dermatologist-developed for sensitive scalps

5. Olaplex No.9 Bond Protector Nourishing Hair Serum

A protective serum designed to shield your hair from pollution, heat, and dullness.

This antioxidant-rich serum detangles, smooths, and creates a protective barrier against everyday stressors, especially in polluted urban environments like Singapore.

Ideal For: Damaged, heat-styled, or city-living hair
Price: $33.80
Key Features:

• Heat protection up to 230°C
• Anti-frizz + detangling
• Silicone-free formula

6. Kérastase Genesis Anti Hair-Fall Fortifying Serum

A daily strengthening serum for breakage-prone hair that needs root support.

Lightweight yet potent, this daily-use serum helps reduce hair fall caused by breakage. It fortifies the roots and boosts scalp resilience for noticeably thicker hair over time.

Ideal For: Weak or breakage-prone hair
 Price: $68.00 (was $85)
 Key Features:

• Fortifies roots and reduces fall
• Hydrating and non-oily
• Use daily for best results

“Especially helpful if your hair snaps during brushing or towel-drying.”

Conclusion: So, Hair Oil or Serum?

At Top Secret, we believe you shouldn’t have to choose between shine and strength, you can have both. 

Hair oils nourish from the inside out, while serums shield and smooth from the outside in. When used together (and correctly), they’re a power duo that protects your strands, no matter the weather or styling stress.

Whether your hair is frizzy, flat, fine, or fried, we’ve stocked our collection with tried-and-tested hair oil and serums from trusted names like Olaplex, Kérastase, Moroccanoil, and Goldwell.

Pair them right, layer light, and your hair will thank you.

Frequently Asked Questions about Hair oil vs Hair Serum

What Is The Difference Between Hair Serum And Hair Oil?

Hair serum is a lightweight, silicone-based product that smooths frizz, protects from heat, and adds shine. Hair oil, on the other hand, nourishes and moisturises hair from within, improving strength and softness over time.

Which Is Better For Frizzy Hair: Oil Or Serum?

Serum is better for smoothing frizz instantly and controlling flyaways. If your hair is also dry or coarse, layer a lightweight oil after for added softness.

How Often Should I Apply Hair Oil Or Serum?

Serum can be used after every wash, while oils are best 1–2 times a week or as needed. Fine hair may require less frequent use.

Can I Apply Hair Oil Or Serum To My Scalp?

Only if the product is designed for scalp use (like Goldwell’s Scalp Specialist). Most oils and serums should be applied from mid-lengths to ends.

What’s The Difference Between Hair Oil And Leave-In Conditioner?

Leave-in conditioners are primarily for detangling and light hydration. Oils deeply nourish and seal moisture, while serums protect and smooth the surface.

Should I Use Hair Oil Or Serum First?

Use hair serum first on damp hair to protect and smooth, then follow with hair oil to lock in moisture and add shine. This layering works best for dry, styled, or colour-treated hair