Thiamine/Yeast Polypeptide: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: June 30, 2025
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We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Thiamine/Yeast Polypeptide?

Thiamine/Yeast Polypeptide is a blend that forms when thiamine, also known as vitamin B1, reacts with small chains of amino acids taken from common baker’s yeast. The result is a water-soluble complex that brings together the vitamin’s energy-boosting nature and the skin-friendly proteins of yeast. Yeast extracts have been used for decades in skincare because they are rich in nutrients that help skin look healthy. Formulators began combining thiamine with yeast peptides when research showed the mix could enhance the soothing effect of each part. Production starts with cultured yeast that is gently broken down to release its polypeptides. These peptides are then combined with thiamine under controlled conditions to create a stable ingredient ready for creams and serums. You will most often see Thiamine/Yeast Polypeptide in moisturizers, anti-aging lotions, sheet masks, brightening treatments and leave-on night creams.

Thiamine/Yeast Polypeptide’s Cosmetic Benefits/Uses

This ingredient is valued for the comfortable feel it gives to many formulas.

Skin conditioning: Thiamine/Yeast Polypeptide helps soften and smooth the skin surface so products feel pleasant during and after use. Regular application can support a healthier-looking complexion by supplying lightweight moisture and reducing the appearance of dryness.

Who Can Use Thiamine/Yeast Polypeptide

Because it is water-based and lightweight, Thiamine/Yeast Polypeptide suits nearly every skin type including dry, normal, combination, oily and even sensitive skin. It does not add heavy oils or pore-clogging waxes so acne-prone users often tolerate it well.

The ingredient is produced from vitamin B1 and baker’s yeast with no animal-derived substances, making it acceptable for both vegans and vegetarians.

Current research shows no specific risks for pregnant or breastfeeding women when the ingredient is applied in cosmetic amounts. Still, this is not medical advice and anyone who is pregnant or nursing should ask a healthcare professional before adding new skincare products.

Thiamine/Yeast Polypeptide does not cause photosensitivity so it will not make skin more reactive to sunlight. Daily sunscreen is still recommended as part of a well-rounded routine.

Potential Side Effects/Adverse Reactions

Side effects from topical Thiamine/Yeast Polypeptide vary from person to person. The points below describe potential reactions that are unlikely for most users when the ingredient is properly formulated.

  • Redness or mild irritation
  • Itching or a stinging sensation
  • Contact dermatitis in individuals allergic to yeast derivatives
  • Rare clogged pores if the overall formula is occlusive

If any of these reactions occur stop using the product and seek advice from a medical professional.

Comedogenic Rating

Rating: 0 (non comedogenic)

Thiamine/Yeast Polypeptide is fully water soluble and contains no heavy oils, waxes or fatty acids known to block pores. Its molecular structure is made up of small peptides and vitamin B1, both of which rinse away easily and sit lightly on the skin. For these reasons it is considered non comedogenic and suitable for people who are prone to acne or breakouts.

Because a finished product’s overall texture also depends on the other ingredients, users with very reactive skin should still pay attention to the full formula, especially if it includes thick butters or occlusive silicones.

Summary

Thiamine/Yeast Polypeptide is a water loving complex that conditions skin by softening the surface and adding lightweight hydration. The vitamin component supports skin vitality while yeast-derived peptides smooth rough patches, helping the complexion appear fresh and healthy.

It is not a headline ingredient in most mainstream lines yet formulators appreciate it for boosting the comfort and slip of moisturizers, serums and masks without raising the risk of clogged pores.

Overall safety is high with very low rates of irritation or sensitization. Even so, it is smart to perform a quick patch test when trying any new product to confirm personal compatibility.

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