Hair Serum: What It Actually Does, What It Doesn't, and How to Pick One Worth Your Bathroom Shelf
Quick answer: A hair serum is a leave-in product you apply to your scalp and hair and don't rinse out, so it's an easy daily step for hair that looks and feels cared for. It's a cosmetic product, not a medicine, so it isn't a substitute for seeing your GP about sudden or significant shedding. Thin Lizzy Xcellerate35 Serum is a spray-on serum with 35 ingredients, including castor oil.
Somewhere between the volumising shampoos, the overnight oils, the gummies and the glossy brochures, the hair aisle stopped making sense. Lots of products promise a lot. Very few explain what they actually do, how to use them, or how you'd even know whether they suit you. So if you've been searching for a hair serum, here's a straight, practical answer: what a serum is, what it can and can't do, and how to choose one worth a spot on your bathroom shelf.
What Is a Hair Serum?
A hair serum is a leave-in product. Unlike shampoo, which spends a minute or two on your head before it's rinsed away, a serum stays put. Scalp serums are usually light sprays or drops you apply at the roots and massage in. Other serums are smoothing products for the lengths, used to tame frizz and add shine.
How Is a Serum Different From Other Hair Products?
- Shampoo: its job is cleaning. It's rinsed off quickly.
- Conditioner and masks: they soften and smooth the lengths, then they're rinsed out.
- Hair oils: they condition the strands you already have, helping them look glossy and feel softer.
- Supplements: taken by mouth, and a balanced diet matters just as much for your overall wellbeing.
- Leave-in serums: applied where you want them and left on, which makes them easy to use every day.
What a Hair Serum Can and Can't Do
A good serum can be a simple, pleasant daily habit that helps your hair look and feel cared for. A scalp serum lets you reach the roots without coating your lengths in heavy product, and massaging it in is a nice few minutes of self-care.
A cosmetic serum isn't a medical product, though. If your shedding is sudden, patchy, comes with a sore or itchy scalp, or started after a new medication or illness, see your GP first. Those changes can have causes a hair care product isn't designed to address.
How to Pick a Hair Serum Worth Your Bathroom Shelf
- Easy to use daily: a serum only helps if you keep using it, so a quick spray beats a complicated ritual.
- Light enough for your hair: fine hair needs a formula that won't leave roots looking greasy or flat.
- Clear instructions: look for a product that tells you how much to use and when.
- Honest wording: be wary of anything promising a "miracle" or instant change. Hair care is a slow, steady habit.
- Real reviews: read a range of customer reviews, not just the top few.
Our Picks
Xcellerate35 Serum
Best for: a quick, spray-on scalp care step you'll actually keep up.
A light spray serum made with 35 ingredients, including castor oil. Spray it onto clean, damp hair, massage it into your scalp and brush through from root to tip so it's spread evenly. The product page suggests 5 to 10 pumps a day. Thin Lizzy's clinical testing reported longer hair after 45 days of daily use. Results vary.
- 35-ingredient formula, including castor oil
- Spray-on, applied to clean, damp hair
- Massage in, then brush through
- Easy to use every day
The Good Hair Brush
Best for: brushing your serum through and detangling gently.
Brushing from root to tip is part of using a scalp serum well. The Good Hair Brush has gentle bristles that work through tangles without pulling, leaving hair feeling smooth.
- Gentle bristles
- Detangles without pulling
- Leaves hair feeling smooth
- Handy for brushing serum through from root to tip
How to Use a Scalp Serum
- Start with clean, damp hair: wash as usual and towel-dry so your hair is damp, not dripping.
- Part your hair: make a few parts so you can reach your scalp.
- Apply at the roots: spray along each part, using the amount on the label.
- Massage in: use your fingertips, with light pressure, for about a minute.
- Brush through: brush gently from root to tip to spread the product evenly.
- Style as normal: keep heat on a lower setting where you can.
- Keep it up: set a daily reminder and take a photo of your parting at the start so you can compare honestly later.
Setting Honest Expectations
Hair care rewards patience. Give any new serum a fair run of consistent, daily use before deciding whether it suits you, and judge it on how your hair looks and feels overall, not just on one day in the mirror. Everyone's hair starts from a different place, so your experience will be your own.
For more, see our Xcellerate35 Hair Serum guide, our thinning hair tips and our article on whether hair oils really make a difference.
What Customers Say
"My wife loves this product she has been using it for a while now"
Shiu M., verified customer (Xcellerate35 Serum)
"Wow! This is the first brush that is so comfortable to use, and quickly takes out any tangles you might have."
Linda T., verified customer (The Good Hair Brush)
"Great hair brush. My partner has coarse curly hair and the brush goes through easily"
Louise N., verified customer (The Good Hair Brush)
Read all Xcellerate35 Serum reviews →
Frequently Asked Questions
Do I apply hair serum to wet or dry hair?
It depends on the product. Xcellerate35 is applied to clean, damp hair, massaged into the scalp and brushed through.
How often should I use a scalp serum?
Follow the label. Most scalp serums, including Xcellerate35, are designed for daily use, and consistency matters more than using a lot at once.
Will a hair serum make my hair greasy?
A light spray serum shouldn't weigh your hair down if you use the recommended amount and focus on the scalp rather than the lengths.
Is Xcellerate35 suitable for men and women?
Yes. Xcellerate35 isn't gender-specific, so anyone in the household can use it.
Can I buy Thin Lizzy hair serum in stores?
Yes. Thin Lizzy is available at Farmers, Life Pharmacy, Chemist Warehouse and Unichem stores across New Zealand. The range can vary by store, so the easiest way to get the full range, bundles and online deals is to shop online. See our FAQ page for stockist details.
Looking for a deal? Many of our best sellers are available in bundle offers from time to time. See our current Bundle Offers →
Final Thoughts
A hair serum isn't magic, and the good ones don't pretend to be. What it offers is a simple daily habit: straight to the scalp, left on, and easy enough to keep up. Choose one you'll actually use, brush gently and give it time.
