Round Lab Birch Juice Sunscreen Review: Sunscreen vs Sun Serum vs Mild-Up (+ Stick)

Everyone searches for “Round Lab sunscreen”, but the brand actually makes several Birch Juice versions, and most reviews cover only one. I have used all four, but I only have the sunscreen, the sun serum and Mild-Up on hand right now, so the side-by-side comparison covers those three, and the stick gets its own bonus section at the end.

I’m not a dermatologist, and this is my own experience on normal skin. For the product facts I used Round Lab’s official store and pointed out where something comes from the brand and not from me.

Key takeaways

• Best overall for me: the sun serum. Light, fast-absorbing, no white cast and the most perfect one under makeup.
• Safest first buy: the regular Birch Juice sunscreen. Thicker, but it glides on and leaves no white cast.
• Mild-Up is thicker, with a slight white cast and a brightening tone-up effect. It is not my favourite, but my mum loves it.
• The stick (bonus, at the end) is light and leaves no trace, but it is the only one I reapply in everyday city life.
• All four were comfortable for my skin: no stinging, breakouts or clogged pores.

The three versions I compare, at a glance

All of them, the stick included, are listed at SPF 50 or SPF 50+ on the US store, and at $24.99 to $25, the price I saw on Round Lab’s own site. Round Lab also lists a PA++++ rating on the sun serum and the stick pages. I bought mine at Olive Young and online on YesStyle, and I own the Korean versions, so the filters on your box may differ from the US list above.

My Round Lab Birch Juice sunscreen review, version by version

Birch Juice Moisturizing Sunscreen: the classic

This is the one most people mean when they say “Round Lab sunscreen”. The texture is dense, but it spreads easily and leaves no white cast at all. For me it is the ideal example of the Korean sunscreen everybody talks about, the one you picture when you search for the best Korean sunscreen that Korean it-girls use.

In city life I never need to reapply it, and a tube lasts me a long time. It never stung my eyes or broke me out.

According to Round Lab’s US product page, the formula is built on spring sap from Inje’s silver birch trees, along with niacinamide, hyaluronic acid and sodium hyaluronate, and it is marketed as a lightweight, non-greasy cream.

Birch Juice Moisturizing Sun Serum: my favourite

This one is my favourite SPF in every season, location and activity. The texture is light and it absorbs quickly. It is the most perfect version under makeup, and it leaves no white cast.

The brand says on the sun serum page that it is SPF 50, PA++++, fragrance-free and made to be applied as the last step after moisturizer. It’s the one I reach for first.

Birch Juice Mild-Up: the tone-up one

Mild-Up is thicker than the regular sunscreen, and it leaves a slight white cast. It is also the only one of the four that brightens the skin, a tone-up effect, which I don’t especially like. My mum, on the other hand, loves sunscreens like this.

On the official Mild-Up page it is described as a mineral sunscreen with zinc oxide, which fits what I see on my skin: a physical filter with a slightly lighter finish.

What’s inside and what it targets

The key ingredients come from Round Lab’s official product pages; the skin-concern notes are my own experience.

Concern	My experience
White cast	None with the sunscreen, sun serum and stick. Mild-Up leaves a light one.
Wearing it under makeup	The sun serum is the most perfect one under makeup.
Sensitive-leaning skin	No stinging in my eyes and no irritation from any of the four.
Breakouts and clogged pores	None for me on normal skin.
Sweat, water and beach days	Water beads up on the surface. I still reapply after swimming.
Scent	None, it feels light.
Oily or very sensitive skin	I haven’t tested these, so I can’t say.

Which one should you buy first?

• You wear makeup or hate any heaviness: the sun serum.
• You want the classic everybody recommends: the regular Birch Juice Moisturizing Sunscreen. I think it will suit nearly everyone, and the same goes for the sun serum.
• You like a brighter, tone-up look: Mild-Up.
• You are out all day and need touch-ups: the stick, in addition to one of the others.

Is Round Lab Birch Juice sunscreen mineral or chemical?

I honestly didn’t know when I started using these, since I judge a sunscreen mainly by how it feels. That’s a common question, so I checked Round Lab’s US store. The regular Birch sunscreen, the sun serum and the stick list chemical filters, while Mild-Up lists zinc oxide, so it is the mineral one.

Filters are not the same everywhere. Round Lab’s own article about the original Birch Juice sunscreen names four filters (Uvinul A Plus, Uvinul T 150, Uvasorb HEB and Tinosorb M), while the US product page for the regular sunscreen lists avobenzone, homosalate and octisalate. Because I use the Korean versions, I always tell people to read the ingredient list on their own box.

Korean vs US versions

I buy the Korean versions. If you are comparing, look at three things: the filter list, the SPF and PA rating, and the name on the packaging, because the same line is sold under slightly different names. For example, the US store sells the regular one as “Birch Moisturizing Sunscreen UVLock”. The filter lists I found for the US store and for the original Korean formula are not the same, which is one more reason to read your own box.

Is it waterproof?

On my skin, yes it behaves that way. You can actually see the water droplets collect on the surface and not soak in, as if there were an oil effect on the water. I wore these on beach days in Bali and Turkey, by the pool and playing tennis in the sun.

The official side is more cautious. The US FDA says no sunscreen is truly waterproof, and that a water-resistant label only has to say whether protection lasts 40 or 80 minutes. So after swimming or sweating, I put more on, no matter how well the droplets bead up.

How I apply it, and how much

My rule is two fingers. I draw a line of sunscreen on my forehead, one down each cheek, and one on my neck, which people forget. Then I spread it over my ears as well, and I put a little on the backs of my hands too, because that skin is thin and shows sun damage and photoaging early.

That matches what the American Academy of Dermatology says: at least about a teaspoon for the face, roughly the length of your index and middle fingers, applied before you go out and reapplied every two hours.

How often I reapply (and my UV widget trick)

In everyday life in the city, I don’t reapply the sunscreen, the sun serum or Mild-Up. Only the stick needs topping up. If I’m in the open sun for a long time, I reapply every 2 to 3 hours, depending on the UV level.

My lifehack: add a UV index widget to your iPhone lock screen. Then you can see at a glance when the UV is high and you actually need to top up.

Round Lab vs Skin1004 Hyalu-Cica and Beauty of Joseon Aqua Rice

I have tried a lot of sunscreens. Skin1004 Hyalu-Cica and Beauty of Joseon Aqua Rice are my other favourites. They are similar to the Round Lab sun serum in how light they feel and how quickly they absorb, and none of them leaves a white cast. Still, the Round Lab sun serum is number one for me.

Round Lab Dokdo toner and Birch Juice cleanser

I’ve also used the Dokdo toner and the Birch Juice cleanser. Both are great base products for any skin type, and a good start if you are just starting skincare or have no real skin problems and want to keep your skin healthy. The ingredient lists are simple and non-irritating, and they slot into any routine, including routines with active ingredients, where they work well as a “connecting” step.

One thing I like about the brand: Round Lab uses only local Korean ingredients, and for each line it shows which part of Korea the main active ingredient comes from. For Birch Juice, the brand’s page says it is spring sap from Inje’s silver birch trees.

The perfect example of the Korean sunscreen everyone talks about.

Bonus: Birch Moisturizing Sun Stick

I don’t have the stick on hand right now, so it is not part of the texture comparison above, and I am keeping this short and to what I know from using it.

The stick is light and leaves no traces on the skin. The trade-off is that it is the only version I have to reapply in everyday city life. I keep it for touch-ups, and the brand says on the stick page that it is made for reapplying over makeup and is travel-friendly.

Who it’s for, and would I buy it again

The regular sunscreen and the sun serum suit pretty much everyone who wants that ideal Korean sunscreen effect. Mild-Up is for tone-up lovers, and the stick is for people who reapply a lot. I haven’t tested them on very oily or very sensitive skin, so I can’t promise anything there.

I will absolutely buy it again, as soon as I finish the ones I have.

If you want to see what goes with it, here is my morning skincare routine, and if sunscreen follows acids in your routine, see my skin guide.

Round Lab Birch Juice sunscreen: common questions

Which Round Lab Birch Juice sunscreen is the best?

For me the sun serum is the best: it is light, absorbs fast, leaves no white cast and sits best under makeup. The regular sunscreen is a close second and a safe pick for almost everyone. Mild-Up is for people who like a tone-up effect, and the stick is for reapplying on the go.

Is Round Lab Birch Juice sunscreen mineral or chemical?

It depends on the version. On Round Lab’s US store, the regular Birch sunscreen, the sun serum and the sun stick list chemical filters, while Mild-Up lists zinc oxide, a mineral filter. Filters can differ between the Korean and US versions, so always check the box you own.

Does Round Lab Birch Juice sunscreen leave a white cast?

Not in my experience with the regular sunscreen, the sun serum or the stick. Mild-Up is thicker than the regular sunscreen and leaves a slight white cast and a brightening tone-up effect, which I personally do not love.

Is Round Lab Birch Juice sunscreen waterproof?

On my skin, water droplets bead up on the surface and do not soak in, so it behaves as if it is waterproof. Officially, though, no sunscreen is truly waterproof. Water-resistant labels are only 40 or 80 minutes, so I reapply after swimming or sweating.

Does it work under makeup?

Yes. The sun serum is the most perfect one under makeup for me, so start there if you wear makeup every day. The brand also says the stick is made for reapplying over makeup.

Do I need to reapply Round Lab sunscreen?

In normal city life I do not reapply the sunscreen, sun serum or Mild-Up. The stick I do reapply. In strong sun I reapply about every 2 to 3 hours depending on the UV index, and the American Academy of Dermatology recommends every 2 hours.

How much should I put on my face?

I use the two-finger rule. The American Academy of Dermatology says at least about a teaspoon for the face, roughly the length of your index and middle fingers. Don’t forget your neck, ears and the backs of your hands.

What is the difference between the Korean and US versions?

The filter lists I found for the US store and for the original Korean formula are not identical. I use the Korean versions. On the US store, filters like avobenzone, homosalate and octisalate are listed, while Round Lab’s own article on the original sunscreen names Uvinul A Plus, Uvinul T 150, Uvasorb HEB and Tinosorb M. Compare the ingredient list on your own box.

Is it good for sensitive skin and oily skin?

My skin is normal, and I had no stinging, breakouts or clogged pores with any of the four. I can’t speak for oily or very sensitive skin, so patch-test first, and ask your dermatologist if you have acne or a skin condition.

Would I buy it again?

Yes, absolutely, as soon as I finish the ones I have.

Sources

• Birch Moisturizing Sunscreen UVLock SPF 50, Round Lab official US store (filters, price, Inje birch sap).
• Birch Juice Moisturizing Sun Serum SPF 50, Round Lab official US store (SPF 50, PA++++, filters with percentages).
• Birch Juice Mild-Up Sunscreen UVLock, Round Lab official US store (zinc oxide, tone-up effect).
• Birch Moisturizing Sun Stick SPF 50+, Round Lab official US store (SPF 50+, PA++++, filters, reapplying).
• Round Lab: the original Birch Juice sunscreen, Round Lab official blog (four UV filters of the original formula).
• Sunscreen: How to Help Protect Your Skin from the Sun, US FDA (broad spectrum, reapplying every two hours, water-resistance labels, no sunscreen is waterproof).
• How to apply sunscreen, American Academy of Dermatology (amount for face, timing, reapplying, ears and neck).

Prices and formulas checked on Round Lab’s US store in October 2026 and can change.