Biome Letter Serum
50ml / 1.7 fl oz
Why most microbiome serums miss the point — and what perioral and periocular skin actually needs
I have sat with more clients managing perioral and periocular dermatitis than I can count, and I hear the same story.
"My steroid cream works, then it doesn't. I stop, and two weeks later it comes back worse. I'm afraid to be without it."
Every time, I think the same thing: we are treating the inflammation. We are not treating what is underneath it.
Steroid-disrupted skin loses something most products never address — its commensal bacteria, the population of organisms that keep the skin's immune response calm and regulated. Suppress that population again and again with topical steroids, and the skin becomes dependent on suppression because the underlying ecosystem never gets the chance to rebuild. That is the cycle. Not a lack of willpower. Biology.
Biome Letter Serum was formulated to interrupt that cycle.
What Biome Letter Serum does
Biome Letter Serum restores microbiome balance in compromised, thin-skinned zones — perioral, periocular, anywhere the skin has been through repeated steroid cycling — without introducing a single live organism.
With consistent use, the inflammatory response calms at the source. Redness and irritation in steroid-cycled zones reduce. The skin barrier, rather than being managed from the outside with occlusion, is genuinely supported to rebuild from within.
There is no fragrance. No essential oils. No live spores. Every ingredient in this formula has one job: restore what steroid use has depleted.
The Korean priori science behind the formula
Most microbiome skincare on the market today uses live bacterial spores — strains like Bacillus subtilis — to physically compete with and crowd out unwanted bacteria on the skin's surface. It is an aggressive approach, and on healthy, intact skin it can work.
But Bacillus subtilis is immunostimulatory by design. It is even used as a vaccine adjuvant for exactly this reason — it provokes an immune response. On skin that is already inflamed, already barrier-compromised, and already cycling through steroid withdrawal, introducing live, immune-activating organisms is not restoration. It is another stressor.
Biome Letter Serum takes the opposite approach: postbiotics, not probiotics. Five ferment lysates and filtrates — Lactobacillus, Lactococcus, Saccharomyces, and two distinct Bifidobacterium strains — deliver the beneficial signaling molecules these organisms produce, without the organisms themselves. No germination. No competition. No immune activation. Just the biochemical instructions that tell the skin's existing ecosystem how to behave.
This is paired with V-Centella Biome, a complex built around Bifida Ferment Lysate and Madecassoside, a pentacyclic triterpene from Centella asiatica with one of the most specific inflammatory mechanisms in clinical skincare. Madecassoside has been shown to directly suppress IL-1β and NF-kB, the two signaling pathways most active in perioral and periocular dermatitis flares. It is not a general calming ingredient. It is targeted at the exact biology driving this condition.
Gentle but giant: five ferment strains, zero live organisms
At a combined 5.5% concentration of postbiotic actives, this is not a trace addition to a basic moisturizer. It is the foundation of the formula.
The Bifida Ferment Lysate fraction carries documented evidence for proliferating Staphylococcus epidermidis, the commensal bacteria most depleted by chronic steroid use and most essential to a stable, non-reactive skin barrier. Ceramides and squalane complete the barrier-repair work, replacing the lipids that inflammation and steroid use strip away.
Nothing here is decorative. Every percentage point is doing clinical work.
How to use Biome Letter Serum
Apply in the evening after cleansing, to the perioral and periocular zones only. A small amount goes a long way — press gently into skin, do not rub.
If you are currently using a topical steroid in these zones, continue as directed by your physician. Biome Letter Serum is designed to work alongside a gradual steroid wean, not as an abrupt replacement. Discuss any change in steroid frequency with your doctor.
Patch test on the inner arm for 24 hours before first use on the face.
Biome Letter Serum
50ml / 1.7 fl oz
Why most microbiome serums miss the point — and what perioral and periocular skin actually needs
I have sat with more clients managing perioral and periocular dermatitis than I can count, and I hear the same story.
"My steroid cream works, then it doesn't. I stop, and two weeks later it comes back worse. I'm afraid to be without it."
Every time, I think the same thing: we are treating the inflammation. We are not treating what is underneath it.
Steroid-disrupted skin loses something most products never address — its commensal bacteria, the population of organisms that keep the skin's immune response calm and regulated. Suppress that population again and again with topical steroids, and the skin becomes dependent on suppression because the underlying ecosystem never gets the chance to rebuild. That is the cycle. Not a lack of willpower. Biology.
Biome Letter Serum was formulated to interrupt that cycle.
What Biome Letter Serum does
Biome Letter Serum restores microbiome balance in compromised, thin-skinned zones — perioral, periocular, anywhere the skin has been through repeated steroid cycling — without introducing a single live organism.
With consistent use, the inflammatory response calms at the source. Redness and irritation in steroid-cycled zones reduce. The skin barrier, rather than being managed from the outside with occlusion, is genuinely supported to rebuild from within.
There is no fragrance. No essential oils. No live spores. Every ingredient in this formula has one job: restore what steroid use has depleted.
The Korean priori science behind the formula
Most microbiome skincare on the market today uses live bacterial spores — strains like Bacillus subtilis — to physically compete with and crowd out unwanted bacteria on the skin's surface. It is an aggressive approach, and on healthy, intact skin it can work.
But Bacillus subtilis is immunostimulatory by design. It is even used as a vaccine adjuvant for exactly this reason — it provokes an immune response. On skin that is already inflamed, already barrier-compromised, and already cycling through steroid withdrawal, introducing live, immune-activating organisms is not restoration. It is another stressor.
Biome Letter Serum takes the opposite approach: postbiotics, not probiotics. Five ferment lysates and filtrates — Lactobacillus, Lactococcus, Saccharomyces, and two distinct Bifidobacterium strains — deliver the beneficial signaling molecules these organisms produce, without the organisms themselves. No germination. No competition. No immune activation. Just the biochemical instructions that tell the skin's existing ecosystem how to behave.
This is paired with V-Centella Biome, a complex built around Bifida Ferment Lysate and Madecassoside, a pentacyclic triterpene from Centella asiatica with one of the most specific inflammatory mechanisms in clinical skincare. Madecassoside has been shown to directly suppress IL-1β and NF-kB, the two signaling pathways most active in perioral and periocular dermatitis flares. It is not a general calming ingredient. It is targeted at the exact biology driving this condition.
Gentle but giant: five ferment strains, zero live organisms
At a combined 5.5% concentration of postbiotic actives, this is not a trace addition to a basic moisturizer. It is the foundation of the formula.
The Bifida Ferment Lysate fraction carries documented evidence for proliferating Staphylococcus epidermidis, the commensal bacteria most depleted by chronic steroid use and most essential to a stable, non-reactive skin barrier. Ceramides and squalane complete the barrier-repair work, replacing the lipids that inflammation and steroid use strip away.
Nothing here is decorative. Every percentage point is doing clinical work.
How to use Biome Letter Serum
Apply in the evening after cleansing, to the perioral and periocular zones only. A small amount goes a long way — press gently into skin, do not rub.
If you are currently using a topical steroid in these zones, continue as directed by your physician. Biome Letter Serum is designed to work alongside a gradual steroid wean, not as an abrupt replacement. Discuss any change in steroid frequency with your doctor.
Patch test on the inner arm for 24 hours before first use on the face.
