E524; Sodium Hydroxide
(in 19,018 products)

Potential Risk Index®:

ISCE InhaleISCE SwallowISCE ContactISCE Environment
PRI Legend


1. Acidity Regulator / Buffering Agent - Changes or maintains the acidity or basicity of food/cosmetics.
2. Antiseptic / Disinfectant - Prevents growth of unwanted microorganisms.
3. Depilatory Agent - Removes unwanted body hair
4. Fragrance / Fragrance Component - Provides or enhances a particular smell or odor.
Sodium hydroxide, also known as lye and caustic soda, is used in many industries: in the manufacture of pulp and paper, textiles, drinking water, soaps and detergents, and as a drain cleaner.
Sodium hydroxide is frequently used as an industrial cleaning agent where it is often called "caustic". It is added to water, heated, and then used to clean process equipment, storage tanks, etc. It can dissolve grease, oils, fats and protein-based deposits. It is also used for cleaning waste discharge pipes under sinks and drains in domestic properties. Surfactants can be added to the sodium hydroxide solution in order to stabilize dissolved substances and thus prevent redeposition. A sodium hydroxide soak solution is used as a powerful degreaser on stainless steel and glass bakeware. It is also a common ingredient in oven cleaners.
In food industry, sodium hydroxide is designated with E number 524. It is used in washing or chemical peeling of fruits and vegetables, chocolate and cocoa processing, caramel coloring production, poultry scalding, soft drink processing, and thickening ice cream. Olives are often soaked in sodium hydroxide for softening; Pretzels and German lye rolls are glazed with a sodium hydroxide solution before baking to make them crisp.
It is approved to use as food additive in EU and generally recognized as safe food substance in US.
EU CosIng Annex III Restriction Information:
(EU) No. 622/2016
Regulated By:
Product Type, body parts:
(a) Nail cuticle solvent
(b) Hair straightener
(c) pH adjuster for depilatories
(d) Other uses as pH adjuster
15d- Callosity softener/remover
Maximum concentration in ready for use preparation:
(a) 5% (5) (b) 1. 2% (5) 2. 4.5% (5) 15d- 1,5% (5)
(b) 1. General use
2. Professional use
(c) up to pH 12.7
(d) up to pH 11
15 d Contains alcakali, Avoid contact with eyes
Keep out of reach of chindren ans Read directions for use carefully
Wording of conditions of use and warnings:
(a) Contains alkali
Avoid contact with eyes
Can cause blindness
Keep out of reach of children
(b) 1. Contains alkali
Avoid contact with eyes
Can cause blindness
Keep out of reach of children
2. For professional use only
Avoid contact with eyes
Can cause blindness
(c) Keep out of reach of children
Avoid contact with eyes
SCCS opinions:
1527/14 - Opinion on Potassium hydroxide (KOH) as callosity softener/remover
Scientific References:
Regulatory References:
1. South Korea - Ministry of Food and Drug Safety - Prohibited/Restricted Chemicals
- Ref: 1175
- Ref: III/15a
3. Argentina Ministerio de Salud - Restricciones
- Hidróxido de sodio o potasio
4. EU Approved Food Additive [2018]
- E524
5. Japan’s List of Designated Food Additives under Article 10 of the Food Sanitation Act
- Sodium Hydroxide (Caustic Soda)
6. Canada List of Permitted Food Additives
- List 8 - Sodium Hydroxide
7. US FDA Generally Recognized As Safe (GRAS) Food Substances (21 CFR 184) [2017]
- § 184.1763 - Sodium hydroxide
8. International Fragrance Association Transparency List [2015]
- Sodium hydroxide

Safety and Hazards (UN GHS):

1. Causes severe skin burns and eye damage (H314)
2. Causes skin irritation (H315)
3. Causes serious eye damage (H318)
4. Causes serious eye irritation (H319)
5. Causes damage to organs (H370)
6. Harmful to aquatic life (H402)

Potential Health Concerns For:

1. Burns, Chemical (PubMed ID:15302423)
2. Disease Models, Animal (PubMed ID:22363499)
3. Esophageal Diseases (PubMed ID:19433192)
4. Eye Burns (PubMed ID:22363499)
5. Eye Injuries (PubMed ID:33358762)
6. Laryngeal Edema (PubMed ID:19433192)

User Comments:

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