E524 · Sodium hydroxide
- WHO
- Safe
- FDA
- Safe
- EFSA
- Safe
- FSANZ
- Safe
- Japan
- Safe
- UK FSA
- Safe
- Health Canada
- Safe
What is E524?
Sodium hydroxide (E524), also known as caustic soda or lye, is used in small controlled amounts in food processing, for example to cure olives, treat pretzels and some baked goods (giving pretzels their characteristic crust), and adjust pH in cocoa processing. It reacts and is largely neutralized during processing, so residual levels in finished food are very low.
Also appears on labels as: Sodium hydroxide, NaOH, Caustic soda, Lye, Food grade sodium hydroxide, Sodium hydroxide solution, Sodium hydroxide pellets, Sodium hydrate, Sodium oxide hydroxide, Industrial grade sodium hydroxide, E524, E 524.
What the evidence says
- Considered safe at the trace residual levels present in finished food; concentrated sodium hydroxide is corrosive, but this is a manufacturing handling concern, not a risk to consumers eating the finished product.
Research behind the verdict
- Safety Assessment of Common Food Additives: Sodium Hydroxide Analysis — Food Safety and Toxicology Research Group, Food Additive Safety and Health Journal (2024). A comprehensive 2024 safety assessment examining sodium hydroxide (E524) among other common food additives, focusing on reproductive, oxidative, and enzymatic perspectives. The study confirmed that sodium hydroxide is safe when used as a pH regulator and processing aid according to approved guidelines. The research noted its effectiveness in food processing applications while confirming adequate safety margins at authorized usage levels. The assessment supports continued use with proper handling and application procedures.[safe]
Frequently asked questions
Is E524 safe?
Our overall verdict for E524 (Sodium hydroxide) is “Safe”, based on the most cautious of the major regulators’ positions — FDA: safe; WHO: safe; EFSA: safe; FSANZ: safe; Japan: safe; UK FSA: safe; Health Canada: safe.
Is E524 vegan, halal or gluten-free?
According to our ingredient data for Sodium hydroxide — vegan: yes, vegetarian: yes, halal: yes, kosher: yes, gluten-free: yes, dairy-free: yes. Manufacturing sources can vary between products; check the label if it matters to you.
What is E524 and why is it used?
Sodium hydroxide (E524), also known as caustic soda or lye, is used in small controlled amounts in food processing, for example to cure olives, treat pretzels and some baked goods (giving pretzels their characteristic crust), and adjust pH in cocoa processing. It reacts and is largely neutralized during processing, so residual levels in finished food are very low.
Does E524 contain allergens?
No known allergens are recorded for Sodium hydroxide.
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This page summarises publicly available regulatory assessments and research. It is general information, not medical advice. Sources: EFSA, FDA, WHO and the studies linked above.