Question 1

What does a face serum actually do that a moisturizer doesn't?

Accepted Answer

A face serum carries a higher concentration of active ingredients in a lightweight, fast-absorbing base, so it delivers targeted treatment (brightening, hydrating, or firming) rather than just sealing in moisture. The One & Done Serum is formulated to be applied after cleansing and before your moisturizer, so actives absorb first.

Question 2

Which serum works best for dark spots and uneven skin tone?

Accepted Answer

Look for a dark spot serum for face use that combines tranexamic acid, niacinamide, and a stable vitamin C derivative, since these three actives target pigmentation through different pathways. The One & Done Serum uses all three together with fermented actives for tone correction, and reviewers on the product page report reduced pigmentation within about a month of use.

Question 3

Is this a collagen serum, or does it just claim anti-aging benefits?

Accepted Answer

It contains multiple peptides, including Copper Tripeptide-1 and Palmitoyl Tripeptide-1, which are commonly used to support the skin's own collagen and elastin production rather than adding collagen topically (topical collagen molecules are generally too large to penetrate skin). This makes it a peptide-based collagen-support serum rather than a direct collagen infusion.

Question 4

How is this different from a Cosrx serum or similar K-beauty actives serum?

Accepted Answer

Many Cosrx serums focus on a single hero ingredient, like niacinamide or snail mucin, in isolation. Terrai's One & Done Serum takes a multi-active approach, layering niacinamide with tranexamic acid, peptides, and fermented ingredients in one formula, so you're not required to layer several single-ingredient serums to get similar coverage.

Question 5

How often should I use this serum, and can I use it every day?

Accepted Answer

Yes, it's designed for twice-daily use, applied as 2 to 3 drops to the face and neck both morning and evening after cleansing. It should be followed by a moisturizer, and SPF is essential in the morning routine since some of the actives (like vitamin C derivatives) can increase light sensitivity.

Question 6

Is this a hydrating serum, or is it more of a treatment serum?

Accepted Answer

It's both. The formula includes sodium hyaluronate, olive squalane, and saccharide isomerate for hydration, alongside treatment actives for pigmentation and texture, which is why it's positioned as an all-in-one rather than a purely hydrating serum.

Question 7

Has this serum actually been clinically tested, or is that just a marketing claim?

Accepted Answer

It has. Terrai publishes an IN-VIVO clinical test report, a hypoallergenic test, and a skin irritation study as downloadable PDFs directly on the product page, which is more documentation than most serums in this price range provide.

Question 8

Is this serum suitable for sensitive or acne-prone skin?

Accepted Answer

The formula has a published in-vivo hypoallergenic test and skin irritation study, which suggests it's formulated with sensitivity in mind. That said, with any new active-rich serum, it's worth patch-testing first, especially if your skin reacts to vitamin C or acid-based ingredients.

Your cart is empty

Your cart

Estimated total

Collection: Skin Care

One & Done Serum

One & Done Serum

Luminous Tinted Sunscreen

Luminous Tinted Sunscreen

Aqua Radiance Sunscreen

Aqua Radiance Sunscreen

Hydra Glow Mist

Hydra Glow Mist

Links