Sea Urchins
A sea urchin spine injury combines mechanical trauma, biological envenomation and a chronic foreign-body reaction. It happens when swimmers or beachgoers accidentally step on or brush against a sea urchin (class Echinoidea). Sea urchins are covered in hundreds of sharp, brittle spines made of calcium carbonate (CaCO₃), along with small venomous pincer organs called pedicellariae. Once in the skin, the calcium spines readily break into many tiny fragments that lodge in the dermis and subcutaneous fat, releasing a purple-black dye that produces a false tattoo (tattooing effect). Without proper care, the neurotoxins and hydrolytic enzymes from the pedicellariae cause sudden, intense pain and tissue swelling, while deeply embedded spine fragments can trigger a chronic foreign body granuloma, tenosynovitis or a dangerous marine bacterial infection.
At Haute-Derma, our management of sea urchin injuries uses dedicated solutions to soften and dissolve the calcium carbonate spines, antibiotics and corticosteroids to bring granulomatous inflammation under control, and modern laser technology to clear tattoo-like pigment and fibrous scarring.
Pathophysiology
How Calcium Carbonate Spines Shatter and Deposit Pigment
- Fragments lodged deep in the skin: sea urchin spines are made of very brittle calcium carbonate. Under pressure (for example, when stepped on), the tip pierces the stratum corneum into the deeper layers and immediately shatters into many small pieces, so trying to pull them out with ordinary tweezers easily breaks them up even further.
- Natural pigment tattooing: many sea urchin species (such as Diadema) have black or purple-black pigment coating their spines. When a spine breaks, this pigment is released into the dermis and forms dark tattoo-like spots that can easily be mistaken for areas of necrosis.
Pedicellariae Venom and the Foreign Body Granuloma Reaction
- Pedicellariae venom: besides the spines, some species have pincer-like pedicellariae that cling to the skin and keep injecting venom containing histamine, serotonin, glycosides and neurotoxins, causing intense throbbing pain, muscle spasms, low blood pressure or a systemic allergic reaction.
- Chronic foreign body granuloma: calcium spine fragments cannot be expelled or dissolved quickly by the tissue. Macrophages and foreign body giant cells surround the fragments and stimulate fibrous tissue growth, forming firm, tender granulomatous nodules, and can lead to tenosynovitis and joint stiffness if the spine is lodged near a finger or toe joint.
Clinical Presentation on the Skin
Acute Phase (Mechanical Injury and Envenomation)
- Purple-black puncture spots: the hallmark is a cluster of round, dark purple or black puncture marks on the skin (caused both by embedded spine tips and by pigment tattooing).
- Intense pain and swelling: the patient feels immediate, severe stabbing pain that spreads and throbs with the pulse. The skin around the punctures becomes swollen, hot and red.
- Signs of marine bacterial infection: after 24–48 hours, the wounds may ooze pus and the swelling may spread due to infection with Vibrio vulnificus or Pseudomonas.
Chronic Granulomatous Phase
- Sea urchin granuloma: appears 2–6 weeks later at the old puncture sites as firm, dark red or purple nodules, 2–8 mm across, mildly tender and persistently itchy.
- Deep complications: spines lodged near a joint can cause synovitis, flexor or extensor tenosynovitis, joint stiffness or a deep tissue abscess.
Emergency Care and First Aid at Haute-Derma
Hot Water Immersion and Dissolving Calcium Fragments
- Immediately soak the injured area in hot water (42–45°C) for 30–90 minutes. The heat helps inactivate the venom proteins from the pedicellariae and rapidly eases the severe pain.
- Soak the area in, or apply gauze soaked with, household vinegar (3–5% acetic acid) 2–3 times a day for 20–30 minutes each time. The mild acid helps dissolve some of the superficial calcium carbonate fragments.
- Important warnings:
- Never dig with a needle, cut the skin yourself or squeeze hard to get deep spines out (this breaks them into even smaller pieces and pushes them deeper into the skin).
- Do not pound or tap the wound with hard objects (a mistaken folk remedy that crushes the tissue and shatters the spines further).
Removing Superficial Spines and Disinfection
- Gently remove any large spine ends clearly sticking out of the skin with sterile tweezers.
- Clean the area with 10% povidone-iodine or chlorhexidine to prevent secondary infection.
Medical Treatment and Cosmetic Repair at Haute-Derma
Antibiotics for Secondary Infection and Medical Treatment of Granulomas
- Oral antibiotics (required if there is pus or the spines are deeply embedded):
- Doxycycline 100 mg twice daily combined with ciprofloxacin 500 mg twice daily for 7–10 days to cover the marine bacteria Vibrio and Pseudomonas.
- Intralesional corticosteroid injection (for chronic granulomas):
- Triamcinolone acetonide (2.5–5 mg/mL) is injected directly into the foreign body granuloma to break down the inflammatory fibrous reaction.
Laser Treatment for Spine Fragments, Tattoo-Like Spots and Skin Repair
- Clearing pigment tattoos and breaking down spines: Q-switched Nd:YAG (1064 nm) or high-energy fractional CO2 laser is used to shatter the purple-black pigment particles in the skin and promote breakdown of remaining spine fragments.
- Restoring the epidermis: a repair cream containing epidermal growth factor (EGF), madecassoside and hyaluronic acid helps close the puncture wounds and prevent hypertrophic or fibrous scars on the soles or fingers.
