Definition

Oxalic acid is a poisonous, colorless substance. It is chemical known as a caustic. If it contacts tissues, it can cause severe damage, such as burning or ulcers, on contact.

This article discusses poisoning from swallowing oxalic acid.

This article is for information only. DO NOT use it to treat or manage an actual poison exposure. If you or someone you are with has an exposure, call the local emergency number (such as 911), or the local poison center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States.

Poisonous Ingredient

Oxalic acid

Where Found

Oxalic acid may be found in some:

• Anti-rust products
• Bleaches
• Metal cleaners
• Rhubarb leaves

Note: This list may not be all inclusive.

Symptoms

Symptoms of oxalic acid poisoning include:

• Abdominal pain
• Burns and blisters where the acid contacted the skin, lips, tongue, and gums
• Chest pain
• Collapse
• Drooling
• Mouth pain
• Seizures
• Shock (rapid drop in blood pressure)
• Throat pain and swelling, which leads to difficulty breathing
• Tremors (unintentional trembling)
• Vomiting

Symptoms from getting oxalic acid on the skin or in the eyes include:

• Burning
• Severe pain
• Vision loss

Home Care

Seek immediate medical help. DO NOT make a person throw up unless told to do so by poison control or a health care professional.

If the chemical was swallowed, immediately give the person water or milk, unless instructed otherwise by a health care provider. DO NOT give water or milk if the person is having symptoms (such as vomiting, convulsions, or a decreased level of alertness) that make it hard to swallow.

If the chemical is on the skin or in the eyes, flush with lots of water (at least 2 quarts or 1.9 liters) for at least 15 minutes.

Before Calling Emergency

The following information is helpful for emergency assistance:

• Person's age, weight, and condition
• Name of the product (ingredients and strengths, if known)
• Time it was swallowed
• Amount swallowed

However, DO NOT delay calling for help if this information is not immediately available.

Poison Control

Your local poison control center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States. This national hotline will let you talk to experts in poisoning. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

What to Expect at the Emergency Room

The health care provider will measure and monitor vital signs, including temperature, pulse, breathing rate, and blood pressure. The person may receive:

• Airway support, including oxygen, breathing tube through the mouth (intubation), and breathing machine (ventilator)
• Blood and urine tests
• Camera down the throat to see burns in the airway (bronchoscopy)
  
• Camera down the throat (endoscopy) to see burns in the food pipe (esophagus) and stomach
• Chest x-ray
• CT (computerized axial tomography) scan
• ECG (electrocardiogram, or heart tracing)
• Fluids through a vein (intravenous or IV)
• Medicines to treat symptoms
• Tube through the mouth into the stomach to aspirate remaining acid if the person is seen shortly after the exposure and a large amount was swallowed

Note: Activated charcoal does not effectively treat poisoning by acids. 

For skin exposure, treatment may include:

• Surgical removal of burned skin (debridement)
• Transfer to a hospital that specializes in burn care
• Washing of the skin (irrigation), possibly every few hours for several days

Hospital admission may be needed. Surgery may be required if the esophagus, stomach, or intestines have developed holes (perforations) from exposure to the acid.

Outlook (Prognosis)

How well a person does depends on the amount of poison swallowed, how concentrated the poison is, and how quickly treatment was received. The faster a person gets medical help, the better the chance for recovery.

Severe damage to the mouth, gastrointestinal tract, or airway may occur and quickly cause death if not treated. Holes (perforations) in the esophagus and stomach may cause serious infections in both the chest and abdominal cavities, which may result in death. Surgery may be needed to repair the perforations.

References

Hoyte C. Caustics. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 143.