Cyanoacrylate Burn Injuries: Two Unusual Cases and a Review of the Literature

The authors present 2 cases of cyanoacrylate glue (“Super Glue”) burns, with a review of the literature and a discussion on the mechanism of action. The authors found all reported cases were with domestic — not medical-grade — cyanoacrylate glue in the presence of cotton fabric. Often erroneously designated as chemical burns, they are thermal burns caused by an intensive exothermic reaction. Cotton acts as a highly potent catalyst, speeding up the polymerization reaction leading to high-peak temperatures capable of causing burns and spontaneous ignition of the fabric. The authors identify factors that explain the different risk profiles of domestic and medical cyanoacrylate glues and could be addressed to improve safety with nonmedical applications.

Cyanoacrylate was first discovered in 1942 by Harry Coover and Fred Joyner at the Kodak research laboratories in Tennessee, but it wasn’t until 1958 that methyl-2-cyanoacrylate (sold under the name “Eastman #910”) was released as the first commercially available cyanoacrylate derivative, or what is commonly termed “Super Glue.”^1-3 Today, 70 years after this discovery, cyanoacrylate glues are widely used in the home and industry as superglue,⁴ in health care as tissue adhesives,^5-9 and in the beauty industry as nail glue to attach artificial nail extensions. Professional nail glues can now be purchased online to be used at home, where accidental spills may occur more frequently than in a professional setting, which was the circumstances of both burns reported herein. 

Cyanoacrylates are organic monomers, which are liquids at room temperature. Combined with weakly alkaline materials, the monomers rapidly polymerize via an exothermic reaction to form a clear, solid, waterproof substance.¹⁰ Curing of the adhesive can be triggered by certain chemicals or electromagnetic radiation (eg, ultraviolet or infrared), but the most common accelerant is water, which provides the hydroxyl ions necessary to bring about the reaction. Some natural fabrics, such as cotton and wool, are known to be potent catalysts of this reaction. Although cyanoacrylate glues are so useful due to the high speed of curing, they can also cause problems: the faster the adhesive cures, the higher the local temperature. 

Figure 1 shows the basic structure of a cyanoacrylate. The molecule is formed by 2 highly polarized subunits, a cyano group and an ester, formed by an acryl acid and a variable alcohol (eg, methanol in methyl-2-cyanoacrylate) and a central carbon atom with a double bond, which breaks during polymerization to form long-chain macromolecules (Figure 2).^10,11 

Case 1
A 2-year-old boy presented to the Burns Unit at Chelsea and Westminster Hospital, London, UK with partial-thickness burns to the chest and abdomen measuring 4 cm x 1 cm and 1 cm x 1 cm. These were mixed-depth burns (superficial partial-thickness and mid-dermal). The child had been playing with a bottle of nail glue, which spilled on his face, chest, and abdomen. The cotton shirt he was wearing at the time adhered to his skin. He did not receive any first aid but was taken immediately to the Accident and Emergency Department (A&E) by his mother, where the shirt was forcibly removed and deroofed the blisters that had formed on his skin. In addition, he had dried glue on his left cheek that had adhered firmly but caused no injury to his skin. A mesh dressing, Mepitel (Mölnlycke Health Care Limited, Lancshire, UK), and nitrofural dressing were applied, and the burn healed within 28 days. 

Case 2
A 13-year-old girl sustained a 4 cm x 6 cm mixed-depth burn to the dorsum of her foot. The burn was mostly mid-dermal with some superficial partial-thickness areas (Figure 3). 

The patient had been using a Chinese nail glue (Figure 4) to attach artificial nails and spilled about 5 mL on her left foot. She had been wearing cotton socks and tights at the time of injury. She felt a burning pain in her foot and saw a dense, white smoke rising from the dorsum of her left foot where the glue had made contact. According to the patient, she quickly removed her socks and tights and applied cold water to the injury for 10 minutes. Afterwards, the patient covered the wound in cling-film and presented to the A&E, where she was referred to the Burns Unit. 

The mesh dressing and ACTICOAT (Smith and Nephew, London, UK) dressing were applied, and her foot was immobilized with a splint. The wound was regularly reviewed for almost 1 month on an outpatient basis (Figure 5), and it healed by day 22. 

A review of the literature revealed several studies concerning the cytotoxic and irritant effects of cyanoacrylate glue and a paper detailing the diverse ocular injuries that occur, but there are only 3 published reports of burn injuries from cyanoacrylate glue (Table 1).^12-15 The first report is of a 2-year-old boy, who spilled cyanoacrylate adhesive on his pajamas.¹⁶ The clothing was forcibly removed in the A&E, causing distress to the child. The second paper reports a burn to the thigh of an 82-year-old man, who was using superglue to make a model airplane, and the patient’s jeans caught fire when glue was spilled on the leg.¹ The third report is of a late presentation of a burn to the thigh in a 28-year-old woman who spilled nail glue on her trousers. The paper describes the burn as a chemical burn rather than a thermal injury.¹⁷ These 3 cases involved full-thickness burns requiring skin grafting, in contrast to the authors’ 2 cases, which were partial-thickness burns. 

The use of cyanoacrylate adhesives in medicine
At the time of their discovery, Coover¹ suggested cyanoacrylate glues could be used as tissue adhesives.¹ Early cyanoacrylates had short-chained alcohol groups (methyl and ethyl cyanoacrylates), and remarkable success was reported during the Vietnam War when they were used as tissue adhesives to obtain closure of solid organs as well as dermal injuries.² Subsequent studies revealed these short-chained cyanoacrylates to be toxic to human tissue since they form high concentrations of cytotoxic products (eg, formaldehyde) when undergoing degradation by hydrolysis.¹⁸ New derivatives with longer chain alcohols were produced for clinical use (Figure 6). The first “second-generation” cyanoacrylate released for clinical use was n-butyl-2-cyanoacrylate, which was sold as Histoacryl (TissueSeal, Ann Arbor, MI) and Indermil (Connexicon Medical, Dublin, Ireland). This did not show cytotoxic effects, but it was brittle and fragile due to the rigid chain formation, especially on highly mobile body areas such as the face or over joints.¹⁸ 

The effects changed with the release of octyl-2-cyanoacrylate (DERMABOND, Ethicon, Somerville, NJ), which was approved by the U.S. Food and Drug Administration (FDA) in 1998. Octyl-2-cyanoacrylate has longer sidechains, which makes it a stronger and more flexible polymer, giving it a breaking strength 4x higher than n-butyl-2-cyanoacrylate.^2,19 Since FDA approval, the applications for the use of cyanoacrylate glues in medicine have expanded greatly, from simple external applications like wound closure or spray dressings to internal applications in surgery or interventional radiology (Table 2). 

Cyanoacrylate glues are commonly used for many purposes. Their potential to cause burns may raise safety concerns about their medical use as tissue adhesives; however, there are only 5 reported incidences of burns, which have all been domestic with either superglue or nail glue.^1,16,17 The authors suspect several factors contribute to glue resulting in a burn.

In all of the reported burn cases, including the authors’, the glue was not in direct contact with the skin but had been spilled on cotton clothing. Cotton is mainly composed of β-linked glucose units, which can provide a large number of hydroxyl groups necessary for the polymerization reaction that occurs during the curing of cyanoacrylate adhesives (Figure 7). The same amount of thermal energy is liberated when a catalyst such as cotton is present, but over a much shorter period of time. The heat cannot dissipate harmlessly through convection and conduction during normal polymerization, which leads to the intense accumulation of heat. Even where present in small quantities, cotton can accelerate the reaction enough to cause spontaneous ignition of the cloth or burn injury, whereas bare skin remains unaffected.^20,21 This is demonstrated in the authors’ first case report, where only the torso — covered by a cotton shirt — sustained a burn, and the face was unmarked. It appears a burn injury only occurs in the presence of a catalyst such as cotton. 

This is observation is supported by several cases where cyanoacrylate glue was ingested.^22-24 In the first,²² a 2-year-old boy bit a tube of superglue, and the glue became adherent to his oral cavity and pharynx. Endoscopy showed no evidence of burns, and bleeding only occurred after the glue was briskly removed, as the child became cyanotic.²² The second case²³ describes the endoscopic removal of superglue from the trachea and bronchi of a toddler, who had aspirated the glue, and again no burns were described.²³ Acids stabilize cyanoacrylates and inhibit polymerization; as unstimulated saliva is slightly acidic (pH 6-7), this may have provided some additional protection against burn injury.²⁴

No warnings had been provided with the nail glues that caused injury to the authors’ patients, but instructions for use and safety datasheets provided with most cyanoacrylates warn that cotton gloves should not be worn.²¹ A greater understanding of the risks and adherence to health and safety protocols may explain why no industrial incidents have been reported. Where reported, the products that caused burns were of low-to-medium viscosity. The lower viscosity increases the risk that a larger amount will be spilled and a greater area affected. Additionally, in the authors’ cases, relatively large amounts of glue had been spilled, about 5 mL. Medical preparations of cyanoacrylate glues are typically ≤ 1 mL.

In summary, the following common factors are noted in the cases where cyanoacrylate glues have resulted in a burn: volume (larger volumes will liberate greater amounts of heat as well as affect a larger area); viscosity (lower viscosity increases the distribution of the glue to affect a larger area); and presence of cotton as a catalyst and the type of cyanoacrylate derivative (those that have shorter alcohol sidechains will cure more quickly and hence reach a higher temperature). 

Tissue adhesives are unlikely to cause thermal injury due to slower polymerization of cyanoacrylates with longer sidechains and smaller volumes used (usually ≥ 1 mL); even if potent catalysts such as cotton were present, the amount of heat generated would be unlikely to cause thermal injury.^16,17,25

As cyanoacrylate glue burns are caused by thermal energy, they should be treated according to standard practice regarding their depth and size, with the only difference being if dried glue has bonded to the skin. Partial-thickness burns were the minimum severity of cyanoacrylate burns in all reported burns cases presented in the A&E; therefore separation of the epidermis takes place, which often sticks to the glue-soaked clothes after curing. Clothing may also stick to areas of normal skin or those with only superficial burns.
Removing clothes forcefully can lift off erythematous as well as blistered skin, increasing the area of skin damage and causing pain and distress for the patient.

Many ways of removing superglue have been reported in both lay and scientific literatures, most of which are ineffective or even harmful to the patient (Table 3). 

Tepid, soapy water can be applied to remove clothing stuck to the skin. A n-butyl-2-cyanoacrylate manufacturer recommends using petroleum gel, saline solution, or 5% solution of sodium bicarbonate.²⁵ Acetone is effective in removing all cyanoacrylate glues but will cause intense, burning pain if applied to broken skin, orifices, or mucosa and should be avoided in these areas. It desiccates undamaged skin so a moisturising cream should be applied after use. Other organic solvents will dissolve the glue but may be hazardous to the patient. Petroleum ether and similar solvents are inadequate. 

Affiliations: Universitäts-Hals-Nasen-Ohren-Klinik, Universität Duisburg-Essen, Essen, Germany; and Burns Unit, Chelsea and Westminster Hospital, London, UK

Correspondence:
Christian P. Eyth, MD
Universitäts-Hals-Nasen-Ohren-Klinik
Universität Duisburg-Essen
45257 Essen, Germany 

Disclosure: The authors disclose no financial or other conflicts of interest.