Sea Snail and Sea Slug Stings
Skin and soft-tissue injury from venomous sea snails and sea slugs (marine gastropod envenomation and dermatitis) covers conditions caused by two main groups of marine mollusks: cone snails (family Conidae) and nudibranchs, the shell-less sea slugs such as Glaucus atlanticus, the blue dragon.
Cone snails carry a microscopic radula tooth that acts like a harpoon, injecting a potent neurotoxic mix called conotoxin directly into the dermis. This causes microvascular paralysis, tissue necrosis and acute respiratory failure. Nudibranchs, by contrast, take up and store the stinging cells (nematocysts) of the Portuguese man-of-war (Physalia physalis) they eat, then discharge them into human skin at a far higher concentration. The clinical picture ranges from contact dermatitis with necrotic blisters and intense burning pain to numbness of the peripheral sensory nerves and stubborn post-inflammatory hyperpigmentation (PIH).
At Haute-Derma, our management of sea slug and sea snail injuries combines first aid to neutralize the toxins, medical treatment to prevent microvascular necrosis, control of nerve-related skin symptoms, and laser therapy to restore the epidermal barrier.
Pathophysiology
The Radula Tooth and Conotoxin (Cone Snails, Conus spp.)
- A microscopic harpoon through the skin: the cone snail strikes by firing a modified, hollow, barbed radula tooth from its proboscis, through the epidermis and deep into the dermis and subcutaneous fat.
- A multi-toxin cocktail: cone snail venom is a complex mixture of hundreds of bioactive peptides (α-, μ- and ω-conotoxins):
- α-conotoxin: blocks nicotinic acetylcholine receptors at the neuromuscular junction.
- μ-conotoxin and ω-conotoxin: shut down voltage-gated sodium (Na+) and calcium (Ca2+) channels in peripheral nerves, causing local vasoconstriction, sudden tissue ischemia and loss of sensory conduction.
Stored Nematocysts Released in Concentrated Bursts (Sea Slugs, Nudibranchs)
- Stockpiling stinging cells in cnidosacs: nudibranchs (such as Glaucus atlanticus) eat venomous jellyfish without digesting their stinging cells. Instead, they move the intact nematocysts into storage sacs (cnidosacs) at the tips of their finger-like appendages.
- Release of porins and a surge of histamine: when skin touches a sea slug, vast numbers of stored nematocysts fire at once, injecting porin toxins that rupture keratinocyte membranes. This causes sudden fluid leakage into the tissue and an acute necrotic contact dermatitis.
Clinical Forms of Skin Injury
Acute Stinging-Cell Dermatitis (Nudibranch / Sea Slug Dermatitis)
- Fire-like burning pain: starts immediately after touching the sea slug. Patients feel an intense, stabbing pain that quickly spreads along the contact area.
- Red streaks and necrotic blisters: red patches form along the line where the sea slug brushed the skin and rapidly erupt into clusters of vesicles and bullae that ooze sticky serous fluid. After 24–48 hours, the center of the blisters may darken with superficial necrosis, followed by widespread peeling.
Neurotoxic Puncture Wounds with Local Ischemia (Cone Snail Stings)
- A pale puncture with central ischemia: a tiny, pinpoint wound whose surrounding skin turns pale at once from intense vasoconstriction, then bluish (cyanosis) as the tissue loses its blood supply.
- Spreading numbness and systemic effects: numbness and tingling (paresthesia) begin at the puncture site and quickly spread through the whole limb. In severe envenomation by the geography cone (Conus geographus), patients may develop drooping eyelids, slurred speech, loss of reflexes and acute respiratory failure within 15–30 minutes.
Emergency Care and First Aid at Haute-Derma
Different Care for Different Culprits (Sea Slugs vs. Cone Snails)
- Sea slugs (nudibranchs):
- Apply household vinegar (3–5% acetic acid) right away for 15–30 minutes to deactivate any nematocysts that have not yet fired.
- Soak the affected skin in hot water (42–45°C) for 20–30 minutes to break down the venom proteins.
- Cone snails (Conus):
- Pressure immobilization technique: wrap an elastic bandage firmly from the end of the limb up past the puncture (with the same pressure used for a venomous snakebite) and splint the limb to slow the spread of conotoxin into the circulation.
- Critical warning: do not use vinegar on cone snail stings (it has no effect). Anyone suspected of a cone snail sting should be taken straight to an emergency/intensive care unit in case breathing support with a ventilator is needed.
Local Wound Cleaning: rinse the wound with 0.9% saline and disinfect it with 10% povidone-iodine. Never rub it with sand or ice.
Medical Treatment and Cosmetic Recovery at Haute-Derma
Preventing Microvascular Necrosis, Calming Allergic Inflammation and Antibiotic Cover
- Treating local ischemia and inflammation:
- A potent topical corticosteroid (clobetasol propionate 0.05%) combined with zinc oxide to settle the blistering dermatitis and reduce tissue swelling.
- Mild peripheral vasodilators and antispasmodics if the fingertips remain persistently bluish.
- Antibiotics to prevent infection with marine bacteria: doxycycline 100 mg twice daily plus ciprofloxacin 500 mg twice daily for 7 days to guard against Vibrio vulnificus and Pseudomonas.
- Controlling systemic symptoms: a second-generation H1 antihistamine (fexofenadine 180 mg) once or twice daily to relieve itching and hypersensitivity reactions.
Resurfacing the Skin and Treating Post-Inflammatory Hyperpigmentation (PIH)
- Healing skin after ruptured necrotic blisters: a serum containing EGF (epidermal growth factor), panthenol (B5), ceramide NP and madecassoside to speed re-epithelialization.
- Treating PIH marks and pigmented streaks:
- Fractional Q-switched Nd:YAG laser (1064 nm) combined with Bio-Light therapy to break up melanin deposits left behind by the necrotic inflammation.
- A 15–20% azelaic acid serum combined with arbutin, niacinamide and stabilized vitamin C to even out skin tone.
