Chemical burn

What is a chemical burn?

Chemical burn is a burn to internal or external organs of the body caused by a corrosive or caustic chemical substance that is a strong acid or base (also known as alkali). Chemical burns are usually the result of an accident and can occur in the home, at school or more commonly, at work, particularly in manufacturing plants that use large quantities of chemicals.

Very mild chemical burns result in irritant contact dermatitis. Chemical burn from a strong acid or alkali is also known as a caustic burn.

What causes a chemical burn?

The main cause of chemical burn is contact with strong acids or bases.

• The strength of acids and bases is defined by the pH scale, which ranges from 1–14.
• A very strong acid has a pH of 1 and may cause a severe burn.
• A very strong base has a pH of 14 and may also cause a severe burn.
• A substance with a pH of 7 is considered neutral and does not burn.

Common acids

Sulphuric acid – concentration ranges from 8% to almost pure acid

• Toilet bowl cleaners
• Drain cleaners
• Metal cleaners
• Car battery fluid
• Fertiliser manufacturing

Nitric acid

• Used in engraving, metal refining, electroplating and fertiliser manufacturing

Hydrofluoric acid – a weak acid and in a dilute form does not burn or cause pain on contact

• Rust removers
• Tyre cleaners
• Tile cleaners
• Glass etching
• Dental work
• Refrigerant

Hydrochloric acid – concentrations range from 5–44%

• Toilet bowl cleaners
• Metal cleaners
• Swimming pool cleaners
• Dye manufacturing
• Metal refining

Phosphoric acid

• Metal cleaners
• Rustproofing
• Disinfectants, detergents
• Fertiliser manufacturing

Common bases

Sodium hydroxide and potassium hydroxide — depending on the concentration — may be very corrosive

• Drain cleaners
• Oven cleaners
• Denture cleaners

Sodium and calcium hypochlorite

• Household bleach
• Pool chlorinating solution

Ammonia

• Cleaners and detergents used in dilute form are not highly corrosive
• Gaseous anhydrous ammonia used in fertilising manufacturing can cause severe burns

Phosphates

• Many household detergents and cleaners

What are the signs and symptoms of chemical burn?

The signs and symptoms of a chemical burn depend on several factors, including:

• pH of the agent
• Concentration of the agent
• Length of contact time
• Amount of agent involved
• Physical form of the agent (ie: solid, liquid, gas)
• Site of contact (e.g. eye, skin, mucous membrane)
• Whether swallowed or inhaled
• Whether or not skin is intact.

Swallowing a solid pellet of an alkaline substance highlights the importance of these factors. The solid pellet sits in the stomach for a longer period, thus more severe burns sustained. Another important factor is concentrated forms of some acids and bases generate a large amount of heat when diluted; this results in a thermal burn as well as a chemical burn.

Some signs and symptoms of chemical burns include:

• Redness, irritation, or burning at the site of contact
• Pain or numbness at the site of contact
• Formation of black dead skin (eschar) — this occurs particularly with acid chemical burns as they produce a coagulation necrosis by denaturing proteins
• Deep tissue injury to the skin is caused by alkali chemical burns, as they produce a liquefaction necrosis that involves denaturing of proteins as well as saponification of fats
• Vision changes or complete loss of vision if chemicals get into the eyes.

Unknown cause 

24 hours after fluoride burn 

10 days after fluoride burn 

In severe chemical burns where the agent has been swallowed, inhaled or absorbed into the bloodstream, the following systemic symptoms may occur.

• Cough or shortness of breath
• Low blood pressure
• Faintness, weakness, dizziness
• Headache
• Muscle twitching or seizures
• Cardiac arrest or irregular heartbeat

What is the management of a chemical burn?

Basic first aid should be administered as soon as a chemical burn has occurred.

• Remove contaminated clothing
• Irrigate the affected area with copious amounts of water. Wash for at least 20 minutes, taking care not to allow runoff to contact unaffected areas. It has been shown that irrigation received within 10 minutes of the burn reduces the severity of the wound and time of stay in hospital.

Chemical burns involving elemental metals (lithium, potassium, sodium and magnesium) should not be irrigated with water as this can result in a chemical reaction that causes burns to worsen. These types of chemical burn should be soaked with mineral oil while waiting for medical attention.

People with minor chemical burns do not require hospitalisation. For more severe burns, patients should receive treatment as for a typical thermal burn patient. In some situations an antidote may be given to counteract the offending chemical agent. For example, hydrofluoric acid burns should be promptly treated with calcium gluconate gel applied every 15 minutes, so the gel should be kept at relevant work sites.

The main treatment aims of burn wound management are:

• Carefully monitor wound
• Keep wounds clean
• Prevent the wound drying out
• Manage secondary infection.

Commonly used topical antibacterials include 1% silver sulfadiazine cream, 0.5% silver nitrate solution and mafenide acetate 10% cream.