Lionfish Stings

Indo-Pacific lionfish (Pterois volitans) have invaded many popular scuba diving locations in the Atlantic and Caribbean. Aside from causing possible harm to swimmers and divers, this voracious predator can dramatically affect populations of native marine animals in the ecosystems to which they have been introduced.

Lionfish are venomous and belong to the Scorpaenidae family. These fish and those of the Synanceiidae family (such as Synanceia, or stonefish) comprise most of the existing venomous fish. Without putting life at risk, envenomations caused by scorpionfish and lionfish can cause significant symptoms due to the systemic action of their venoms.

A lionfish was speared because they are a dangerous species.

Lionfish have spines that are covered by an epithelial sheath containing venom-producing glands in the grooves of the upper two-thirds of the long and slender spines. The dorsal fin has 12-13 rays or spines, the pelvic fin has two, and the anal fin has three. When the ray of the fin penetrates the victim’s skin, venom flows to the wound. Possible contact with various marine life occurs during diving, fishing and food handling. Even though most fish stings are benign, some lionfish stings require urgent medical treatment.

Puncture wounds by lionfish can cause pain lasting for several hours, rapid edema (swelling) and subcutaneous bleeding. Swelling typically clears in two to three days, while the tissue discolorations can last up to five days. In some cases swelling can become so severe that blood flow is compromised, possibly leading to tissue necrosis (tissue death), which can be common in fingertips. A secondary complication is wound infections. Lionfish venom is not lethal to healthy humans, and we are not aware of any published reports of death.

A man shows his swollen hand compared to his non-swollen hand. The right hand is very puffy.

Envenomations are rare even in areas where lionfish are common, but recognition of the fish is important to prevent injuries. In Cozumel, we have gathered six years of data encompassing 107 cases for which we recorded the following symptoms in order of frequency: pain, erythema (redness), edema, local heat, blisters, necrosis (dead tissue), nausea, vomiting, dyspnea, fever and muscular weakness. Limb paralysis and cardiac failure are infrequently observed.

We have recorded only two complications from lionfish envenomations: one due to thermal burn (and later infection) when applying hot water to the sting area and one case of decompression sickness resulting from a diver reacting with a rapid ascent after being stung. The injuries we recorded did not pose risks of cardiovascular failure or death in our patients. The most important symptoms were the local inflammation and severe pain. We did not observe in our patients some signs and symptoms sometimes reported with lionfish envenomations; we recorded only four cases each of blisters and necrosis. In our opinion, most of the systemic signs we found were related to pain.

A man holds two dead lionfish above a cooler chest full of ice.

In the past two years we have seen a significant reduction in the number of lionfish envenomation victims seeking medical assistance, likely because people are now more familiar with lionfish and proper first aid for stings — and also because the park has reported fewer lionfish sightings after an intensive program to control them began five years ago. DAN® has provided information about how to treat lionfish injuries, working in conjunction with Arrecifes de Cozumel National Park to distribute thousands of first-aid information cards over the past five years. Informed divers are able to reduce contact with lionfish and increase their ability to manage injuries when they occur.

Responding to a Lionfish Sting

An infographic from DAN on how to manage a lionfish sting while diving.
  • Clean the wound by thoroughly washing the area with soap and fresh water. Remove any foreign material, and control bleeding.
  • Control the pain by immersing the affected area in the hottest water tolerable without causing injury — the upper limit is 113°F (45°C) — for 30 to 90 minutes. Have someone test the water on the same area as the injury to ensure it is not too hot, as intense pain may impair one’s ability to discriminate between hot and scalding. Repeat as needed.
  • Apply cold packs or ice later to reduce swelling and help with pain.
  • Take pain control medication, if needed.
  • Apply topical antibiotic, if available.
  • Seek a professional medical evaluation; medical management may include sedatives, a tetanus vaccination and antibiotics.
  • If severe symptoms are present, call 911 or your local emergency medical services number.
  • Call the DAN 24-hour emergency hotline at +1-919-684-9111.
© Alert Diver — Q3 2018