33,172 reviews

custom hair serum

3oz - $19
  • A lightweight finishing product that helps enhance shine, smooth frizz + flyaways, and increase your hair's overall manageability.
  • Formulated with a hair-healthy blend of argan, jojoba, and sunflower oils, and a custom blend of natural ingredients depending on your hair goals.
  • 100% customizable and designed to work specifically for your unique hair type and goals.
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All Function of Beauty products are formulated without sulfates, parabens, phthalates, mineral oils, or gluten. Our products are also all certified vegan and cruelty-free.


recommended use

Warm a small amount of product in your hands and apply to wet or damp hair. Using your fingers, distribute the product evenly from the mid-shaft to ends, working your way through the length of your hair. Make sure to avoid the roots. Do not rinse out, and style as you’d like!


great for...

Hair serum is recommended for those who are looking to tame frizz and add an added boost of shine to their hair. It is specially formulated for your unique hair goals and needs, making it a great option for all hair types, although it is particularly recommended for those with coarse, curly, and/or coily hair types.

the people have spoken

The above testimonials were shared by customers who received a sample as part of our testing group.

got questions?

How does the serum work?

Our serum creates a light film that coats the damaged cuticles to make hair appear less frizzy while also preventing moisture loss. This film also reflects light and gives hair shine and luster (aka that gorgeous glass hair look).

Will it make my hair oily?

Your customized hair serum is meant to be applied to the ends and mid-shaft, avoiding the scalp entirely. If you’re using the small recommended amount, it should not make the hair oily. Be sure to also start with just a small amount and add more only where needed!

Can I use it in addition to leave-in treatment?

Yes, leave-in treatment and serum are a great pair! Our leave-in treatment protects, hydrates, and conditions the hair, while the serum seals in the moisture and provides a glossy finish with ingredients like argan oil, jojoba oil, annatto oil, and sunflower oil.

How often should I use it?

You can use the hair serum as often as you like; just be sure to avoid your roots while styling!
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