Siero Filler ISDIN Firming Serum: 30-Day Test Results

Cult Verdict
This Spanish pharmacy serum went viral for instant plumping — but does it actually rebuild collagen after a month?
Expert Analysis · Honest Reviews · Real Results
1.🔬The 10-Second Plump

So this ISDIN serum went viral last summer because people claimed it literally fills in lines instantly — think injectable-lite, but in a dropper bottle. I called bullshit.

The instant effect is real. But here’s the thing nobody talks about: that “filler” effect is just glycerin swelling your top layer of skin. The collagen rebuild takes weeks. I wanted to know if the long game actually paid off.

2.💉What You’re Actually Buying

It’s a milky, almost watery serum with a strange blue tint — like someone diluted a Gatorade. $69 for 30ml. The claim: visible firming in 28 days, backed by clinical testing.

1

Texture

Thinner than water, thicker than toner — absorbs in literally 8 seconds flat.

2

Scent

None. Zero. Like they forgot to add fragrance — which I actually prefer now.

3

Packaging

Blue glass dropper that looks expensive on your shelf but is a pain when you’re rushing.

white and clear glass container on brown wooden table

Photo: Poko Skincare / Unsplash

3.📆Ingredients That Actually Do Stuff

The hero is a synthetic peptide complex plus hyaluronic acid — the usual suspects. But the surprise? They added a marine collagen fragment small enough to actually penetrate. Most collagen serums are a lie. This one might not be.

  • Palmitoyl Tripeptide-1: Signals fibroblasts to make new collagen
  • Hydrolyzed Marine Collagen: Small enough to absorb, firming after 2 weeks
  • Sodium Hyaluronate: Plumps instantly, lasts about 6 hours
  • Glycerin: The real MVP for that ‘filler’ look
a person holding a bottle

Photo: Laura Jaeger / Unsplash

4.🔍30 Days of Testing

First pump felt like nothing — it vanished into my skin before I could spread it. I actually reapplied because I thought I missed. By day 3, my morning puffiness was noticeably less.

Week 2-3: my nasolabial folds looked softer, not gone, but softer. What surprised me? It didn’t break me out — most peptide serums give me tiny whiteheads. This one didn’t.

💡

One Thing: Apply to damp skin — it spreads 3x further and you’ll use half the product per session.
three beautiful young women standing next to each other

Photo: Brayden Prato / Unsplash

5.💬The Verdict

After 30 days: my skin is firmer — not “lifted” like a facelift, but the sag under my jawline tightened by maybe 15%. The instant plumping still happens every time I apply, which is the real trick. Lines didn’t disappear, but they looked shallower in good lighting.

Buy if
You’re 35+ with early sagging and want a visible-but-subtle boost without needles
⏭️

Skip if
You have oily skin that hates silicones — this has a light film finish
💰

Worth it?
For the instant effect alone, yes. The collagen part is a bonus, not a miracle.
6.Final Word

It’s a good serum that does exactly what it promises — just don’t expect to look 25 again. The viral hype is 60% deserved, 40% marketing fluff.

7.8/10
Good plump, real firming, fair price
🛍️

Where to Buy: Amazon or the brand site — get the travel size first to test your skin’s reaction, then commit to the full bottle.