Chemical burns can be caused by acids or bases that come into contact with tissue. Acids are defined as proton donors (H+), and bases are defined as proton acceptors (OH-). Bases also are known as alkalis. Both acids and bases can be defined as caustics, which cause significant tissue damage on contact. The strength of an acid is defined by how easily it gives up the proton; the strength of a base is determined by how avidly it binds the proton. The strength of acids and bases is defined by using the pH scale, which ranges from 1-14 and is logarithmic. A strong acid has a pH of 1, and a strong base has a pH of 14. A pH of 7 is neutral.
Most acids produce a coagulation necrosis by denaturing proteins, forming a coagulum (eg, eschar) that limits the penetration of the acid. Bases typically produce a more severe injury known as liquefaction necrosis. This involves denaturing of proteins as well as saponification of fats, which does not limit tissue penetration. Hydrofluoric acid is somewhat different from other acids in that it produces a liquefaction necrosis.
The severity of the burn is related to a number of factors, including the pH of the agent, the concentration of the agent, the length of the contact time, the volume of the offending agent, and the physical form of the agent. The ingestion of solid pellets of alkaline substances results in prolonged contact time in the stomach, thus, more severe burns. In addition, concentrated forms of some acids and bases generate significant heat when diluted or neutralized, resulting in thermal and caustic injury.
The long-term effect of caustic dermal burns is scarring, and, depending on the site of the burn, scarring can be significant. Ocular burns can result in opacification of the cornea and complete loss of vision. Esophageal and gastric burns can result in stricture formation. An oral burn is shown in the images below.
View Image | Caustic oral burns. |
View Image | Caustic burns of tongue. |
A large number of industrial and commercial products contain potentially toxic concentrations of acids, bases, or other chemicals that can cause burns.[1, 2] Some of the more common products are listed as follows:
Sulfuric acid is commonly used in toilet bowl cleaners, drain cleaners, metal cleaners, automobile battery fluid, munitions, and fertilizer manufacturing. Concentrations range from 8% acid to almost pure acid. The concentrated acid is very viscous and more dense than water. It also generates significant heat when diluted. These attributes make sulfuric acid an effective drain cleaner. Concentrated sulfuric acid is hygroscopic. Thus, it produces dermal injuries by dehydration, thermal injury, and chemical injury.
Nitric acid is commonly used in engraving, metal refining, electroplating, and fertilizer manufacturing.
Hydrofluoric acid is commonly used in rust removers, tire cleaners, tile cleaners, glass etching, dental work, tanning, semiconductors, refrigerant and fertilizer manufacturing, and petroleum refining. This is a weak acid, and, in dilute form, it will not cause immediate burning or pain on contact.
Hydrochloric acid is commonly used in toilet bowl cleaners, metal cleaners, soldering fluxes, dye manufacturing, metal refining, plumbing applications, swimming pool cleaners, and laboratory chemicals. Concentrations range from 5-44%. Hydrochloric acid is also known as muriatic acid.
Phosphoric acid is commonly used in metal cleaners, rustproofing, disinfectants, detergents, and fertilizer manufacturing.
Acetic acid is commonly used in printing, dyes, rayon and hat manufacturing, disinfectants and hair wave neutralizers. Vinegar is dilute acetic acid.
Formic acid is commonly used in airplane glue, tanning, and cellulose manufacturing.
Chloroacetic acids
Monochloroacetic acid is used in the production of carboxymethylcellulose, phenoxyacetates, pigments, and some drugs. It has significant systemic toxicity because it enters and blocks the tricarboxylic acid cycle, inhibiting cellular respiration. It is highly corrosive.
Dichloroacetic acid is used in manufacturing chemicals. It is a weaker acid than trichloroacetic acid, and it does not inhibit cellular respiration.
Trichloroacetic acid is used in laboratories and in chemical manufacturing. It is highly corrosive and "fixes" tissues it contacts. It does not inhibit cellular respiration.
Phenol and cresols
Phenol, also known as carbolic acid, is a weak organic acid used in the manufacture of resins, plastics, pharmaceuticals, and disinfectants.
Cresols are dihydroxybenzenes that are used as wood preservatives, degreasing agents, and chemical intermediates. These substances are very irritating to the skin and can be absorbed through the skin to produce systemic toxicity.
Sodium hydroxide and potassium hydroxide are used in drain cleaners, oven cleaners, Clinitest tablets, and denture cleaners. They are extremely corrosive. Clinitest tablets contain 45-50% sodium hydroxide (NaOH) or potassium hydroxide (KOH). Solid or concentrated NaOH or KOH is more dense than water and generates significant heat when diluted. Both the heat generated and the alkalinity contribute to burns.
Calcium hydroxide also is known as slaked lime. It is used in mortar, plaster, and cement. It is not as caustic as NaOH, KOH, or calcium oxide.
Calcium oxide, also known as quicklime, is the caustic ingredient in cement. It generates heat when diluted with water and can produce a thermal or caustic burn.
Sodium and calcium hypochlorite are common ingredients in household bleach and pool chlorinating solution. Pool chlorinators also contain NaOH and have a pH around 13.5, making them very caustic. Household bleach has a pH around 11 and is much less corrosive.
Ammonia is used in cleaners and detergents, as a fertilizer, and as an industrial cleaner and sterilizing agent. The dilute form is not highly corrosive. Gaseous anhydrous ammonia is used in a number of industrial applications, particularly in fertilizer manufacturing. It is very hygroscopic (has a high affinity for water). It produces injury by desiccation and heat of dilution, in addition to causing a chemical burn. It can cause severe skin burns as well as pulmonary injury if inhaled.
Phosphates commonly are used in many types of household detergents and cleaners. Substances include tribasic potassium phosphate, trisodium phosphate, and sodium tripolyphosphates.
Silicates include sodium silicate and sodium metasilicate. They are used to replace phosphates in detergents. Dishwashing detergents are alkaline, primarily to builders such as silicates and carbonates. They are moderately corrosive.
Sodium carbonate is used in detergents. It is moderately alkaline, depending on the concentration.
Lithium hydride is used to absorb carbon dioxide in space technology applications. It vigorously reacts with water to generate hydrogen and lithium hydroxide. It can produce thermal and alkaline burns.
Bleaches
Chlorites are the primary chemicals used as bleaches in the United States. Household bleach is alkaline with a pH of 11-12, but it is dilute enough that it is minimally irritating to the skin. More concentrated, industrial strength chlorites may be more damaging to the skin.
Peroxides
Peroxides are commonly used in hair dyes. Household-grade hydrogen peroxide (3%) produces minimal-to-no skin irritation. Concentrations of 10% may cause paresthesias and blanching of the skin. Concentrations of 35% or more will cause immediate blistering.
Chromates
Potassium dichromate and chromic acid are common industrial chemicals used in tanning, waterproofing fabrics, corrosion inhibitor, painting, and printing, and they are also used as an oxidizing agent in chemical reactions. Chromates can result in severe skin burns and subsequent systemic toxicity, including renal failure.
Manganates
Potassium permanganate is a strong oxidizing agent that is used in dilute solutions as a disinfectant or sanitizing agent. In dilute solutions, it is minimally irritating to the skin. In concentrated form or pure crystals, it can cause severe burns, ulcerations, and systemic toxicity.
White phosphorus
This chemical is used as an incendiary in the manufacture of munitions, fireworks, and fertilizer. White phosphorus is spontaneously oxidized in air to phosphorus pentoxide, giving off a yellow flame and a dense white smoke with a garlic odor. After explosions of munitions or fireworks, small particles of phosphorus can become embedded in the skin and continue to smolder.[3]
Metals
Elemental lithium, sodium, potassium, and magnesium react violently with water, including water on the skin.
Hair coloring agents
Hair coloring agents contain persulfates and concentrated solutions of peroxides. Straightening agents may contain concentrated alkali. Chemical burns can result if these are not diluted properly or have a prolonged contact time with the scalp. Burns with various products have been reported in the literature.[4]
Airbag injuries
The rapid inflation of airbags is accomplished through the rapid decomposition of sodium azide to produce nitrogen gas. The sodium generated then reacts with potassium nitrate and silicon dioxide to produce gas. In the second step, small amounts of sodium hydroxide and sodium carbonate are generated. Airbags can produce abrasions, lacerations and contusions through the physical force of the rapid expansion. They can also produce alkaline chemical burns. These are especially concerning when corneal abrasions occur due to airbags.[5]
These agents are primarily chemical warfare agents and are also known as blister agents. They include sulfur and nitrogen mustards, arsenicals, and phosgene oxime. For more information see CBRNE – Vesicants, Mustard: Hd, Hn1-3, H and CBRNE – Vesicants, Organic Arsenicals: L, ED, MD, PD, HL.
United States
Burns are a common problem seen in the emergency department. There has been a decrease in the number of burns in the United States through 2000, but this appears to have stabilized since. Most burns are only partial thickness and occur on the extremities. Approximately 5% of individuals with burns presenting to the ED require admission.[6]
In 2011, the American Association of Poison Control Centers (AAPCC) reported 15,616 cases of exposures to acidic substances, 18,960 cases of exposures to alkaline substances, 20,518 cases of peroxide exposures, and 38,613 cases of bleach exposures. During that time, 352 cases of exposure to phenols or phenol products were reported.[7] Chemical injuries account for 2-6% of burn center admissions.[3]
International
Worldwide, corrosive substances are commonly used for chemical assault. The most common substances used are lye and sulfuric acid.[8, 9, 10]
Assaults with caustic chemicals worldwide are more likely to occur against women.[8]
Adults and children are nearly equally exposed to caustic chemicals. Adults exposed to industrial strength chemicals often suffer more severe burns.
The prognosis depends entirely on the extent of tissue injury. Small lesions heal well, whether dermal or esophageal. Larger dermal burns can produce significant scarring. Extensive esophageal lesions can result in future stricture formation. Hydrofluoric acid burns can cause progressive tissue injury and may result in loss of digits.
Even moderate corneal burns can result in scarring and loss of vision. Sometimes this can be remedied by corneal transplantation.
In the 2011 report of the American Association of Poison Control Centers, exposures to acids and acid-containing products and chemicals resulted in 8 deaths, 78 cases of major toxicity, and 1270 cases of moderate toxicity. Exposures to alkali products and chemicals resulted in 4 deaths, 136 cases of major toxicity, and 1995 cases of moderate toxicity. Exposures to peroxides resulted in no deaths, 13 cases of major toxicity, and 226 cases of moderate toxicity. Exposures to bleaches and hypochlorite-containing products resulted in 22 cases of major toxicity and 968 cases of moderate toxicity. Exposures to phenol-containing products resulted in 47 cases of moderate toxicity.[7]
For cases of occupational exposure, educate the patient on the proper safety precautions that should be taken when working with hazardous materials. All industries are required to inform employees of any dangerous materials they may come into contact with in the workplace and must provide them with adequate training and protective equipment.
When children experience chemical burns, counsel the parents on how to keep medications and chemicals out of the reach of children. Parents may not think that something like automatic dishwashing detergent can be a danger to children. Inform them of the various substances in the home that are potentially dangerous. Consultation with the local social services agency may be indicated to evaluate the child's home situation.
For patient education resources, visit the First Aid and Injuries Center.
Clinical signs and symptoms vary depending on the route of exposure and the particular substances involved. Because of the variety of presentations, emergency clinicians must be prepared to handle all possibilities. Some exposures, such as hydrofluoric acid, may present without immediate pain and should be considered in patients with complaints of slow-onset deep pain occurring after exposure to an appropriate product.
Patient history should include the following:
For children presenting with chemical burns a thorough history of the situation should be obtained, considering possible neglect and/or abuse. Children may be exposed to caustic substances in methamphetamine labs.
If the exposure was by ingestion, the immediate concern is to protect the patient's airway. If there is evidence of airway compromise (eg, oropharyngeal edema, stridor, use of accessory muscles), consider establishing a definitive airway.
In dermal exposures, consider the following:
In ocular exposures, consider the following:
In the presence of periorbital dermal lesions, consider the following:
For ingestions, consider the following:
Scarring, infection, and poor healing may occur with dermal burns. Skin grafting may be required.
Ocular burns, especially from alkali substances and hydrofluoric acid, can result in cataract formation and/or complete vision loss.
Perforation and/or bleeding and respiratory compromise from upper airway edema are the short-term complications of caustic ingestions. Stricture formation is the main long-term complication associated with caustic burns to the esophagus.
Laboratory studies depend on the burn type and extent of exposure.
For severe burns, consider the following:
For localized burns, usually no laboratory tests are required.
For hydrofluoric acid burns, consider the following:
For ingestions of caustics, consider the following:
For oxalic acid burns, check calcium.
For chromic acid burns, consider the following:
For monofluoroacetic acid burns, consider the following:
For phenol burns, consider the following:
For ingestions, consider the following:
Endoscopy for ingestions is as follows:
Check the pH for any chemical exposure to the eye or for airbag injuries.
Endotracheal intubation is required for severe respiratory symptoms. Direct visualization is recommended to assess the degree of injury.
Bullae resulting from chemical burns should be decompressed and debrided.
Prompt wound irrigation is the most critical aspect in limiting the extent of dermal burns from exposure to caustic substances. Animal studies have shown that irrigation of both acid exposures and alkaline exposures within several minutes decreases the pH change in the skin and the extent of dermal injury. A burn center case series found that patients who received irrigation within 10 minutes had a 5-fold decrease in full-thickness injury and a 2-fold decrease in length of hospital stay.[13]
Prevent contaminated irrigation solution from running onto unaffected skin.
Remove contaminated clothes.
If contamination with metallic lithium, sodium, potassium, or magnesium has occurred, irrigation with water can result in a chemical reaction that causes burns to worsen. In these situations, the area should be covered with mineral oil and the metallic pieces should be removed with forceps and placed in mineral oil. If forceps are not available, soak the area with mineral oil and cover it with gauze soaked in mineral oil.
If contamination with white phosphorus has occurred, thoroughly irrigate the area with water then cover the area with water-soaked gauze. Keep the area moist at all times. The area can also be covered with petroleum jelly.
If eye exposures have not been irrigated, then this should be started immediately. Immediate removal of caustic substances in the eye is critical.[14]
The first priority in treatment is to ensure complete removal of the offending agent. Thorough decontamination is key. Adequate irrigation is difficult to define and depends on the amount of exposure and the agent involved. Using litmus paper to measure the pH of the affected area or the irrigating solution is helpful. Complete removal and neutralization of concentrated acids and alkalis may require several hours of irrigation. Tap water is adequate for irrigation. Low-pressure irrigation is desired; high pressures may exacerbate the tissue injury.[13, 15, 16, 17] An analysis of 13 studies showed that diphoterine, a hypertonic, amphoteric, polyvalent, and chelating solution, may be superior to other rinsing solutions for cutaneous and ocular chemical burns, but further study is required.[18]
If a question of airway compromise exists, secure the airway.
Large surface burns require the same fluid therapy as that for thermal burns.[19] See Emergent Management of Thermal Burns.
After initial decontamination, the full extent of the injury must be ascertained and the patient must be treated as a typical burn patient. Based on the degree of injury, ensure adequate fluid resuscitation and take precautions to prevent complications (eg, hypothermia, infection, rhabdomyolysis).
Elemental metals
The elemental forms of lithium, potassium, sodium, and magnesium react with water. If these metals are thought to be on the skin of a patient, do not irrigate with water. Cover the area with mineral oil. The metallic pieces should be removed manually with forceps and placed in a container of mineral oil.
White phosphorus
Keep the area immersed in water and manually remove any phosphorus particles seen. Visualization under a Wood's lamp may aid in detection and removal of retained phosphorus particles.[3]
Phenol
Polyethylene glycol 300 or 400 and isopropyl alcohol have been recommended for the removal of phenols and cresols. If skin damage has already occurred, isopropyl alcohol may be very irritating. Polyethylene glycol should be diluted with water to form a 50:50 ratio prior to using. One study showed polyethylene glycol no more efficacious than copious water irrigation for phenol exposures.[20]
Vesicants
See CBRNE – Vesicants, Mustard: Hd, Hn1-3, H and CBRNE – Vesicants, Organic Arsenicals: L, ED, MD, PD, HL for emergency department care.
Hydrofluoric acid burns
These burns require special consideration. They should initially be treated as any other burn, with thorough irrigation. However, due to the penetrating power of the fluoride ion, specific neutralization procedures are indicated.[21] Fluoride can be neutralized by either calcium or magnesium. For small superficial burns, topical calcium or magnesium gels can be applied. Deeper burns usually require subcutaneous injections of calcium gluconate. Hand burns can be difficult to manage; these burns can be treated with subcutaneous injections of calcium, intra-arterial calcium infusions, or intravenous infusions of magnesium. Keeping the hand warm and adequately treating pain will help to increase local circulation and the body's natural supply of calcium and magnesium.[22]
No objective studies comparing intra-arterial calcium to other treatments have been done. Studies on animals demonstrated that intravenous magnesium is as effective or more effective than subcutaneous injections of calcium in treating local hydrofluoric acid burns. When local treatment of hydrofluoric acid burns is not possible, this treatment is safe and should be considered.[23]
Ocular exposures [14]
The goal for decontamination should be to achieve a pH (of the eye wash) of at least 7.3, preferably 7.4. If the pH remains below this, check the pH of the irrigating solution. The pH should be rechecked 30 minutes after irrigation has been completed.[24, 25]
If pH paper is not available, an adequate guideline is decontamination with 2 L of irrigation fluid over 30-60 minutes. A Morgan lens is recommended for irrigation. Use a topical anesthetic prior to use.
Caustic ingestions
Gastric emptying is contraindicated. Activated charcoal is not useful and may interfere with subsequent endoscopy. Dilution with milk or water is contraindicated if any degree of airway compromise is present. Milk may interfere with subsequent endoscopy. Water is benign. Some substances, such as drain cleaners containing sulfuric acid or sodium hydroxide, generate heat when diluted with water. Local areas of heat generation can be minimized by diluting with a moderate quantity of fluid (250-500 mL).[26, 27, 28]
Do not attempt to neutralize the caustic agent. Neutralizing the caustic agent may generate excessive heat from the exothermic reaction of neutralization.
Admission is recommended for large surface area or circumferential dermal burns, for burns by substances with systemic toxicity, or for pain control.
Following caustic ingestions, admission is recommended for any patient with oral burns; any patient who is symptomatic; or any patient who ingested a strong acid, or base, hydrofluoric acid, or other highly caustic substance.
Transfer all significant dermal burns that cannot be handled locally to a regional burn center. Always decontaminate the burn area, initiate fluid resuscitation, and administer analgesic agents prior to transfer.
Patients with any significant scleral or corneal injury should be transferred to a facility where ophthalmologic care is available. Always irrigate the eyes prior to transfer.
If endoscopy is not available and the patient is symptomatic, has oral burns, or has ingested a potentially caustic substance, transfer the patient to a facility that can perform endoscopy. Since endoscopy does not need to be performed on an emergent basis, observation of asymptomatic patients is acceptable.
For severe dermal burns, consult a general surgeon or a burn service. Burns to the hands, face, or perineum may require the appropriate specialties.
Ophthalmologic consultation is recommended for patients with ocular burns from acids or bases if there is any significant degree of corneal or scleral injury.[24, 25]
Caustic ingestions may require multiple specialties, including gastroenterology, GI surgery, ENT, and pediatric surgery for children.
Consult a psychiatrist for cases of attempted suicide.
For cases of pediatric exposure, counsel the family on keeping dangerous substances out of the reach of children.
For suicide attempts, consult a psychiatrist.
In many states, the Occupational Safety and Health Administration (OSHA) requires reporting of industrial injuries. Employers should provide the necessary training and protective equipment for employees working with potentially hazardous materials.
Dermal burns treated on an outpatient basis should be rechecked every 2-3 days.
Any ocular burns treated as on an outpatient basis should be rechecked in 24 hours.
Endoscopic examination of all transmucosal or transmural esophageal burns should be repeated in 2-3 weeks.
Medications have a limited role in the treatment of most chemical burns. Topical antibiotic therapy is usually recommended for dermal and ocular burns. Calcium or magnesium salts are used for hydrofluoric acid burns. Pain medications are important for subsequent burn care.
Steroid therapy is controversial for caustic ingestions but may be helpful for treating upper airway inflammation. No evidence indicates that steroid therapy decreases incidence of stricture formation. Steroids may predispose the patient to infection and may mask signs of perforation. There has been some use of aloe products on mild burns; however, currently, no definitive information on their use for chemical burns is available.[27, 29]
Nonsteroidal anti-inflammatory agents do provide some degree of pain relief for mild burns by inhibition of prostaglandin mediators. These have not been evaluated for chemical burns and should be avoided in all cases of GI burns from ingestions.
After decontamination is performed on patients with chemical burns affecting a significant portion of the body, administer standard IV fluid and narcotic therapy as used for thermal burns. For additional information, see the Emergent Management of Thermal Burns article.
Significant dermal burns require adequate IV fluid resuscitation and analgesics (eg, morphine sulphate). Consider the use of patient-controlled analgesia pumps.
Clinical Context: Silver sulfadiazine is used topically for dermal burns and is useful in the prevention of infections from second- or third-degree burns. It has bactericidal activity against many gram-positive and gram-negative bacteria, including yeast.
Clinical Context: Erythromycin ophthalmic is used prophylactically to prevent infections following ocular burns. The ointment has a very low incidence of allergic reactions. Other possible agents include polymyxin B, bacitracin, and ciprofloxacin solutions.
Clinical Context: This agent is used topically for dermal burns and is useful in the prevention of infections from second- or third-degree burns. It has bactericidal activity against many gram-positive and gram-negative bacteria, including yeast. It is preferable for the face and visible areas.
Topical and ophthalmic antibiotics are routinely used for dermal and ocular burns, respectively. The injured tissues lose many of their protective mechanisms and are at increased risk of infection.
Clinical Context: Morphine sulfate is the drug of choice for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone. Morphine sulfate administered intravenously may be dosed in a number of ways and is commonly titrated until the desired effect is obtained. During the ED treatment of the acute burn, use it intravenously (preferred) or intramuscularly for moderate or severe pain.
Clinical Context: This drug combination indicated for the relief of moderate to severe pain. It is the drug of choice for aspirin-hypersensitive patients. Formulations of oxycodone/acetaminophen are available as follows: Tylox-5/500, Percocet-5/325, Percocet-7.5/500, Percocet-10/650.
Clinical Context: This drug combination is for outpatient use and is indicated for the relief of moderate to severe pain. Formulations of hydrocodone/acetaminophen are available as follows: Vicodin-5/500, ES-7.5/750, HP-10/600 Lorcet-10/650, Plus-7.5/650 Lortab-2.5/500, 5/500, 7.5/500, 10/500 Norco-10/325. A typical elixirs contain 2.5 mg hydrocodone and 167 mg/mL acetaminophen.
Clinical Context: Ibuprofen is usually the drug of choice for the treatment of mild to moderate pain, if no contraindications exist. It inhibits inflammatory reactions and pain by decreasing the activity of the enzyme cyclooxygenase, resulting in the inhibition of prostaglandin synthesis. It is useful for outpatient oral use where nonsedating drugs are preferred. It also has the advantage of an anti-inflammatory effect.
Clinical Context: Ketoprofen is used for the relief of mild to moderate pain and inflammation. Initially administer small dosages to patients with a small body size, elderly patients, and those with renal or liver disease. When administering this medication, doses higher than 75 mg do not increase therapeutic effects. Administer high doses with caution, and closely observe the patient for response.
Clinical Context: Naproxen is used for the relief of mild to moderate pain. It inhibits inflammatory reactions and pain by decreasing the activity of the enzyme cyclooxygenase, resulting in a decrease of prostaglandin synthesis.
Pain control is essential to quality patient care. Analgesics ensure patient comfort and have sedating properties, which are beneficial for patients who have sustained injuries to the eye.
Morphine is recommended in the ED. For outpatient treatment, combinations of hydrocodone or oxycodone and acetaminophen are usually sufficient. Codeine is not recommended. Patients placed on opiate analgesics should be cautioned not to drive or operate machinery.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are most commonly used for the relief of mild to moderate pain. Although effects of NSAIDs in the treatment of pain tend to be patient specific, ibuprofen is usually the drug of choice for initial therapy. Other options include flurbiprofen, ketoprofen, and naproxen.
Clinical Context: Polyethylene glycol is used as an aid in removing phenol or cresols. The desired agent is PEG 400 mixed 50:50 in water. Most hospitals are not likely to have this product. If it is not available, use bowel-cleansing products containing PEG.
These agents can help remove offending substances from the skin and minimize their caustic effects.