Source: https://verify-veg.com/blog/l-cysteine-in-bread/
Language: en

# L-Cysteine (E920): Human Hair and Feathers in Bread?

"Human hair in bread" sounds like an urban legend, but it points at a real ingredient with a real
history. L-cysteine, a dough conditioner used in commercial baking, has traditionally been
extracted from animal and human sources, including hair and feathers. Today the picture is more
complicated, because much of it is made in a lab instead.

> **Key Takeaways**
> - L-cysteine (E920) is an amino acid used to soften dough and speed up industrial bread-making.
> - It has traditionally been extracted from human hair, duck feathers and pig bristles.
> - Modern production is increasingly synthetic or fermentation-based, which is vegetarian and vegan.
> - The label rarely tells you which source was used, so the ingredient is usually ambiguous.

**TL;DR: L-cysteine (E920) is a dough conditioner that was traditionally made from human hair,
duck feathers or pig bristles.** Today much of it is synthetic or fermentation-produced, but the
label almost never says which one you are getting.

## What L-cysteine does

L-cysteine is an amino acid, and in baking it acts as a dough conditioner. It breaks down gluten
slightly, which makes dough more extensible and easier to machine-shape at high speed. The Baking
Association of Canada describes it as an additive that softens dough and shortens mixing time in
commercial bread production
([Baking Association of Canada](https://www.baking.ca/wp-content/uploads/2019/12/L-Cysteine.pdf),
retrieved 2026-08-25). That is why it turns up in bagels, pizza dough, tortillas and mass-produced
breads rather than in a slow sourdough.

## The source problem

The ingredient's reputation comes from its origin. Historically, L-cysteine was extracted from
keratin-rich animal material, including human hair collected from salons, duck feathers and pig
bristles. The Vegetarian Resource Group documented this plainly when explaining why L-cysteine is
a concern for vegetarians and vegans
([Vegetarian Resource Group](https://www.vrg.org/blog/2013/04/22/information-about-l-cysteine/),
retrieved 2026-08-25).

That source is why the ingredient is controversial, and why "hair in bread" keeps making headlines.

## Why it is usually ambiguous now

Manufacturing has changed. A large share of L-cysteine is now produced by fermentation or
synthesis, which is vegetarian and vegan. The catch is that food labels list it as "L-cysteine" or
"E920" without saying how it was made. So a loaf of bread could contain hair-derived cysteine,
fermentation-derived cysteine, or a mix, and the consumer cannot tell from the label alone.

This is the rare case where the *ingredient* is not the problem so much as the *opacity* of the
label.

## How to check

1. Look for breads labeled **vegan** or **no animal-derived ingredients**, which rules out
   hair-derived cysteine.
2. Note that "E920" or "L-cysteine" with no further detail is ambiguous.
3. Choose artisan or sourdough breads, which usually skip dough conditioners entirely.
4. Scan the product. A scanner app flags E920 and other ambiguous additives against your diet.

L-cysteine is one of several ingredients where the label hides more than it reveals. See our
[E-numbers cheat sheet](/blog/e-numbers-vegan-list/) for the rest.

## The bottom line

L-cysteine has a genuinely gross history, but modern production makes it a coin flip rather than a
certainty. If you need to be sure a bread is vegan, the label alone usually cannot tell you, so
look for a vegan mark, buy artisan, or let a scanner check it.

**Check before you eat.** The Verify Veg app scans a barcode or reads an ingredient list from a
photo and flags ingredients against your diet (vegan, vegetarian, halal, kosher, Jain and more).
[Download on the App Store](https://apps.apple.com/us/app/verifyveg-vegan-scanner/id6758276834) -
Android is coming soon.

*Written by Samir Narain, founder of Verify Veg. Verify Veg helps people check packaged food
against their diet by scanning barcodes and reading ingredient lists from photos.*

*Note: Verify Veg provides ingredient-based compatibility checks, not certification. Ingredient
sources can vary by manufacturer, so always confirm with the brand or vendor.*