Guidance

Sodium hydroxide: general information

Updated 28 November 2024

Overview

Sodium hydroxide is a white, odourless solid at room temperature. It is available in solid form as lumps, pellets or chips and as a solution. It is also commonly known as caustic soda and soda lye.

Uses of sodium hydroxide

The main use of sodium hydroxide is in the production of other industrial chemicals. It may be used as an industrial cleaner and degreaser. It is also used in the pulp, paper, metal, food and textile industries, in water treatment processes and various household products including de-scalers and drain cleaners. Sodium hydroxide is also used in the production of soaps, mineral oils and rubber.

How sodium hydroxide gets into the environment

Sodium hydroxide may enter the environment during its production and use. However, it does not persist in the environment.

Exposure to sodium hydroxide

The general population may be exposed to very small amounts of sodium hydroxide due to its use in domestic cleaning products although these sources are unlikely to cause harm if used correctly.

Workers employed in industries that produce, or use, sodium hydroxide may be exposed to higher levels of sodium hydroxide than the general population. However, safe levels are enforced to protect employees who may be exposed to sodium hydroxide at work. Such levels are below those that are thought to cause harmful effects.

How exposure to sodium hydroxide could affect your health

The presence of sodium hydroxide in the environment does not always lead to exposure. In order for it to cause any adverse health effects, you must come into contact with it. You may be exposed to sodium hydroxide by breathing or ingesting it, or by skin contact with it. Following exposure to any chemical, the adverse health effects by which you may encounter depend on several factors, including the amount to which you are exposed (dose), the way you are exposed, the duration of exposure, the form of the chemical and if you were exposed to any other chemicals.

Low level exposure from the correct use of household products that contain sodium hydroxide would not be expected to cause adverse health effects.

Breathing in sodium hydroxide causes irritation of eyes, nose and throat, cough, chest tightness, headache, fever and confusion. In serious cases damage to the airways, a fast heart rate and eye damage can occur. An accumulation of fluid in the lungs may occur and may take up 36 hours to develop.

Ingestion causes immediate burning of the mouth and throat, breathing difficulty, drooling, difficulty swallowing, stomach pain and vomiting (there may be blood in the vomit). In serious cases there may be damage to heart, lungs, kidneys and blood.

Dilute solutions may not be corrosive to the skin but can be irritating. Skin contact with stronger solutions can cause pain, burns and ulcers. Eye contact causes pain, twitching of the eyelids, watering eyes, inflammation, sensitivity to light and burns.

Sodium hydroxide and cancer

Sodium hydroxide is not thought to be a cancer-causing chemical.

Vulnerable people

Individuals with breathing problems such as asthma may be more susceptible to the effects of inhaled sodium hydroxide. This is because sodium hydroxide can cause irritation of the airways leading to chest tightness, wheezing and breathlessness.

Pregnancy and the unborn child 

Low level exposure from the correct use of products that contain sodium hydroxide would not be expected to harm to the unborn child.

There is limited information about over exposure to sodium hydroxide during pregnancy. The irritant/corrosive tends to occur at the point of contact, for example, irritation to the skin or eyes. The absorption of alkali compounds into the body is generally low and therefore they do not cause effects in other parts of the body. Therefore, sodium hydroxide is unlikely to have a direct effect on the unborn child. However, if the exposure sodium hydroxide the mother to become unwell this may affect the health of the unborn child.

Children

If children breathe, ingest or touch sodium hydroxide they will have similar effects to those seen in adults. Sodium hydroxide containing products in the home should be stored in an appropriate container and kept out of the reach of children.

What to do if you are exposed to sodium hydroxide

Low level exposure from the correct use of products that contain sodium hydroxide would not be expected to cause any adverse health effects.

Please see below for advice following all other exposures to sodium hydroxide:

You should remove yourself from the source of exposure.

If you have got sodium hydroxide on your skin, remove soiled clothing (not over the head), wash the affected area with lukewarm water and soap for at least 10 to 15 minutes and seek medical advice.

If you have got sodium hydroxide in your eyes, remove contact lenses, irrigate the affected eye with lukewarm water for at least 10 to 15 minutes and seek medical advice.

If you have inhaled or ingested sodium hydroxide, seek medical advice.

Additional sources of information

NHS Choices – Acid and chemical burns

Email [email protected] if you have any questions about this guidance or [email protected] if you have any other questions.

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