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 • Hair  • Haircare Reviews  • Is Function of Beauty’s Custom Serum a Fluffy Hair Game Changer?
Reviewing Function of Beauty's custom Hair Serum

Is Function of Beauty’s Custom Serum a Fluffy Hair Game Changer?

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I don’t know if I’m the only one but so far the change in seasons is taking something of a hit on my hair.

I’m not sure if that’s because the weather changed quite suddenly where I live or because my hair just enjoys being fluffy…Either way, it’s suddenly a lot drier and also double the size it was two weeks ago (and sadly not at the roots).

The resulting triangle of frizz hasn’t been helped by the fact that I accidentally dyed my hair *just a tiny bit* orange with a new gold shampoo I was trying out last week, which has meant I’ve now washed it approximately 50,0000 times to get it back to its original colour.

And while rootling through the menagerie of hair care products I keep on permanent standby for such a hair-related disaster I came across my custom-made Function of Beauty Hair Serum.

A product that had fallen out of my regular routine mainly because I had opted for the floral scent which I’m not the biggest fan of, I had vague memories of this being heavy enough to tame my ridiculous mane yet lightweight enough to add shine – not grease – and I thought it might help out my now dry hair.

But could it tame my mane of frizz? Read on to find out.


Is Function of Beauty's Custom Serum a Fluffy Hair Game Changer?

Image – @functionofbeauty/Instagram



This is new, up-to-date information. We updated this article in April 2024 to add our further thoughts on Function of Beauty’s hair serum, complete with updated prices.


What is Function of Beauty’s Hair Serum?

But first up, some background (because Function of Beauty’s completely custom approach to haircare can be a little bamboozling to anyone who hasn’t ordered from them before).

Made by US-based custom haircare brand Function of Beauty (a total game changer for the fluffy-haired like me), this serum represents a world first for being the only one that is personalised to your specific hair type.

Following the same process as when ordering the brand’s custom Shampoo and Conditioner, ordering starts with a quick quiz about hair thickness, type, and the goals you are trying to achieve.

You can pick up to five goals out of a possible 16. Since my hair is pretty much unmanageable to begin with (even before I start loading it with highlights) I always go for the same; shine, anti-frizz, deep condition, shine, straighten and hydrate.


Reviewing Function of Beauty's custom Hair Serum

Image – Live That Glow


You can also pick the fragrance you want (out of a possible 8 choices), as well as what name you’d like added to your bottle (possibly the best and most exciting bit of the whole process is owning a load of bottles with your name on – I don’t know why but honestly it really is).

With Function of Beauty’s Shampoo, Conditioner and Hair Mask you also have the option to pick the colour of your products (and even mix and match shades if you like for something of a psychedelic bathroom display), but alas the hair serum is only available in the one shade – a pale gold.

Since this is a personalised treatment the ingredients included in each product will be different for most people – and tailored to what you want to get out of the treatment.

My own blend contains silicone, safflower oil, argan oil, vitamin E, and baobab seed oil.

Function of Beauty claims the resulting custom serum can reduce frizz by up to 70 per cent, improve shine 26 times more than untreated hair, and protect hair from thermal damage up to 400°F.


Function of Beauty’s Hair Serum review

A fairly thick serum, this really does help to weigh down my massive hair and offers a great shine.

I only wish I’d stuck with my normal scent of Peach rather than a floral one. Not because the floral scent isn’t nice if you like sweet fragrances (it’s really quite feminine and pretty), but because it’s just not my favourite (and because I love the Peach option so much I don’t think I’ll ever stray from it again).

But while this does add control and shine, does it do the job better than say a £5 serum from the pharmacy…? I think it depends on what you’re hoping to get out of it.

Because, if you want a ton of hair-nourishing ingredients then this has them by the boatload.  =But if you just want something silicone-based and heavy enough to de-frizz then there are certainly high street options that will do the job with less of a price tag.

Having said that, anyone who loves the scents that are unique to Function of Beauty will like the ability to carry the scent from their custom shampoo and conditioner through to the rest of their haircare.

Equally, for those who want to use only the best of the best ingredients that are targeted at their particular hair needs at every step of their haircare routine, then this is for you.


Is Function of Beauty's Custom Serum a Fluffy Hair Game Changer?

Image – @functionofbeauty/Instagram


What other people have to say

Customers on the Function of Beauty Instagram page have great things to say about their custom serums, with one writing “I LOOOOVE this hair serum!! My hair has never felt so soft”.

Another called their serum “dreamy”, while another customer says “Function serum is literally the best!”


How to use it

Unlike Function of Beauty’s really quite excellent Leave-In Conditioner which is combed through wet hair, this is designed to be used through dry or towel-dried hair.

The brand recommends using half a pump to one pump of the serum on short hair, and one to two pumps for medium hair or long hair. 

I have a lot of hair so I find I use at least two pumps most times. Still at 87 ml here I don’t get through much product so it’s lasting me ages.

I also like using this as a final step post-styling, as well as for topping up between hair washes to keep frizz at bay.

Is Function of Beauty's Custom Serum a Fluffy Hair Game Changer?

Image – @functionofbeauty/Instagram


The takeaway

Do I like this serum? Yes – it does a great job of taming and smoothing my hair. Are there high-street alternatives that also do a brilliant job though?  Yes, absolutely.

Having said that, there will definitely be people who are willing to trade off the price here against the potential benefits of a fully customised product.  Equally, the scents you can pick here are both proprietary to Function of Beauty and quite lovely, so you may even like this product for the custom scent factor alone.

For me, I’ll probably carry on re-buying my beloved IGK Mistress, which is also silicone-based and contains a load of hair-friendly ingredients and UV filters (and that yummy scent!).  I also love Gisou’s Honey Infused Hair Oil.

But, what I will absolutely continue using though is my *absolutely brilliant* Function of Beauty custom shampoo, conditioner and leave-in conditioner, which have single-handedly made most hair days good ones, and called off my years-long search for the perfect products to suit my own fluffball hair.

Great for: Anyone who wants to treat multiple hair concerns in one go, with one product. This serum will also appeal to anyone who likes a glass hair-style shine.

Not-so-great for: Already very healthy hair, since these personalised products are great for my damaged hair, but those whose hair is already in good condition might not need such focused/personalised attention.

Function of Beauty’s Hair Serum is £33.00 on Function of Beauty UK/$29 on Function of Beauty US



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Sally Underwood is a journalist, *serious* beauty fan, and Editor-in-Chief of Live That Glow. Formerly Editorial Director of one of Europe's largest newspaper groups, Sally has been a beauty obsessive since her teen years spent dragging her long-suffering (but immaculately-groomed) friends around every beauty counter in London. She now leads Live That Glow's editorial operations.

Expertise: Skincare, Body care
Education: University College London

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