These two products often get bundled together and confused as being the same thing, but they’re designed to do very different (and very helpful) jobs. Understanding the difference between hair oil and hair serum means you can choose what your hair actually needs, not just what sounds nice on the label.
At UpCircle, we believe in simple routines, planet-friendly formulas, and results you can feel. So let’s break it down properly.
What is hair oil?
Hair oils are usually made from nourishing plant oils – think argan, coconut, jojoba, or rosemary oil. Their main purpose is to nourish and condition by working inside the hair strand.
Using hair oils
Hair oils don’t just work on the surface of your hair; they infuse deeply to protect, hydrate, and strengthen your strands.
Natural oils work to create a lightweight barrier to lock hydration inside the hair shaft. This helps to keep dryness and frizz at bay while sealing in moisture. Oils add softness and shine while reducing breakage and the amount of split ends, by coating the cuticle (the outer layer of your hair) and smoothing your hair.
Healthy hair doesn’t start with your strands; it starts with your scalp! Using natural hair oils that are rich in fatty acids and vitamins hydrates the skin at the root, which balances dryness and excess oil production. Your hair’s natural defences can also be weakened by heat styling, UV rays, and pollution. To protect from damage, natural hair oils work to form a protective layer to minimise the impact of that stress.
From a smoother texture to stronger strands or greater shine, a well-chosen oil can transform both how your hair looks and how it feels – which is equally important.
When applying your hair oil, consistency is key.
Start with dry or slightly damp hair to help the oil spread more evenly. Make sure you don’t completely saturate your hair, as soaking wet hair can prevent absorption. Our top tip is to lightly mist your hair with water before applying.
- Apply a generous amount directly onto your hair, focusing on the scalp, roots and ends.
- Gently massage into your scalp for two to five minutes. Use your fingertips in small circles to help boost microcirculation and encourage growth.
- Work through mid-lengths and ends. Focus on the driest areas (usually the ends) for maximum nourishment.
- Leave the oil on for a minimum of 20 to 30 minutes, or overnight for an intensive treatment. Wash and style as usual.
With hair oil, you don’t need much – start with a few drops and build up if needed. It’s always easier to add more than to try to rinse away excess later.
Check out our blog post on how to apply hair oils for more handy tips.
When to use a hair oil
- As an overnight mask
- Pre-wash as a conditioning treatment
- Post-wash on damp hair to lock in moisture
- On dry ends to soften and reduce brittleness
They’re particularly helpful for dry, frizzy, textured, heat-damaged, or colour-treated hair – basically, any hair that needs a little extra love.
What is a hair serum?
Hair serums are lightweight treatments designed to sit on the surface of your strands. The best serums contain ingredients that coat and smooth the hair cuticle to add shine, shield against frizz and damage, and prevent moisture loss.
Unlike rinse-out conditioners or pre-wash hair treatment oils, serums are typically applied to damp or dry hair and left in, meaning their effects can last until your next wash.
Are you keen to dive deeper and learn more about what hair serums actually are? We dedicated an entire blog to the subject! Here is an overview of what you need to know.
What do hair serums do?
A good hair serum with naturally nourishing ingredients helps to:
- Reduce frizz by smoothing the strand cuticle.
- Add softness and shine for a healthy gloss.
- Protect from heat if they include ingredients that act as a barrier against heat damage.
- Guard against humidity, pollution, and general day-to-day wear.
A hair serum is your finishing step to bring your look together; it’s the product that gives your hair that polished, glossy look.
We make some claims about our Hair Serum: that it offers proven heat protection and some serious anti-breakage power, and that's because it does! See our clinical trial results.
Using a hair serum
You can use hair serum for different purposes, depending on when in your routine to use it. Smooth over dry or nearly dry hair before styling for softness and shine – especially if you’re styling with heat! Apply after styling your locks if you’re hoping to tame frizz.
- Start small and only use one to three pumps of the serum, depending on your hair length and thickness.
- Apply to mid-lengths and ends only, to avoid weighing down your roots or making them look greasy.
- Distribute the product evenly using your fingers or a wide-tooth comb to spread the serum through your hair.
- Style as usual: Blow-dry, straighten, or leave to air-dry.
Because serums are lightweight, they work for all hair types, even fine hair that gets weighed down easily.
Top tip: For an extra-smoothing effect, try warming the serum slightly between your palms before applying to your hair.
Hair oil vs hair serum
Key differences
The difference between hair oil and hair serum comes down to where they work and what they’re trying to help with.
- Hair oils absorb into the strand, nourishing it from the inside. They help to increase nourishment, strength and softness.
- Hair serums coat the outside to smooth, protect, and add shine. They help to boost sleekness, frizz control, and add instant shine.
Think: oils care for the long-term health of your hair, while serums perfect the finish.
Can you use hair serum and hair oil together?
Absolutely. Hair oils and serums can be layered because they do different jobs. The key is to apply them in the right order:
- Hair oil first (on damp hair) for nourishment.
- Hair serum last (on dry or nearly dry hair) for smoothing and protection.
Our Hair Serum + Hair Oil Duo gives you long-term hydration and a frizz-free, glossy finish.
Both products have their place; you just need to know what you’re trying to achieve. Whether you're nourishing with an oil or smoothing with a serum, the right choice is the one that aligns with your hair’s needs that day.
Discover our full range of natural haircare at UpCircle.