Chemical burns are common injuries seen in the ED, but some potentially caustic agents are not obvious. The ash residue which remains after wood is burned contains variable amounts of potassium hydroxide and potassium carbonate. The solution of lye that results from wood ash soaked or boiled in water is a strong alkali used to make soap from rendered fat. Those unfamiliar with this process may view ashes as harmless. We report a skin exposure to wood ash and water that rapidly produced superficial burns in a toddler.
- Wood ashes alone are said to be nontoxic.
- A poultice application of wood ash and water is touted as a folklore-remedy for pain relief.
- Wood ash plus water create a strong alkali that is capable of burning human skin.
- Wet wood ash can cause full thickness burns and necrosis given sufficient skin contact time.
A 2-year-old boy was playing with his water gun in cold wood ash left in an outdoor wood-burning stove. Afterwards, he complained of pain but no itching and his mother noted redness over his hands, arms, and thighs. She administered diphenhydramine and called the pediatrician, who advised bathing with soap and water. She was then referred to the poison center. Photographs of the injured sites sent electronically to the poison center showed multiple, confluent, poorly-defined erythematous lesions interspersed with punctate lesions over the dorsal aspect of the hands, the posterior forearm, and the anterior thighs, bilaterally. Some of the larger lesions appeared to be edematous but no blisters were noted.
Day 0 – Superficial burns to forearm and anterior thigh
The working diagnosis was acute contact dermatitis due to some component of the ash. Over-the-counter hydrocortisone cream was recommended to minimize inflammation, and antibiotic ointment for soothing and protection. The lesions improved significantly overnight. By the fourth day post-exposure, the skin on the thighs had returned to normal and there were scattered small eschars on the hands and fingers. One site over the base of the thumb showed a healing ulceration from a deeper lesion.
Day 4 – Healing lesion at base of thumb, hand
While wood ashes are considered nontoxic, they contain alkaline material in the form of potassium carbonate and potassium hydroxide, often referred to as pearl potash and potash, respectively. These compounds are very soluble in water and react with water to release hydroxide ions which can produce a pH as high as 12. This alkaline solution is capable of causing clinically significant burns. There are only a few cases of such burns in the literature and these were quite severe. Most resulted in full thickness burns and necrosis which required surgical debridement and skin grafting. The alkaline potential of wood ashes diminishes after their first encounter with rain since it readily leeches out the caustic compounds. This may be one reason that burns that come to medical attention are an unusual occurrence. Despite the toddler having only brief skin contact with wood ash splashed with water, the exposure caused unexpected superficial burns.
While chemical exposures causing acute irritant contact dermatitis are relatively frequent cases in the ED, this case should alert poison centers and ED providers and nurses of the association of chemical burns with wood ashes and water.
Unusual toxicology cases such as this wood ash exposure may be difficult to identify and diagnose. Our advice is to call the Missouri Poison Center where specially trained nurses, pharmacists, and medical toxicologist can provide you with the most up-to-date management advice on common and uncommon exposures.