Dissolving Sea Urchin Spines

Dissolving Sea Urchin Spines

If you’ve ever stepped on a sea urchin you know how difficult it can be to remove the spines that get left behind in your foot, like tiny splinters ranging from the size of one strand of hair to some measuring 1/8” in diameter. They can go in about a half inch deep, and they hurt.

Made up mostly of calcium carbonate, the strands can break off easily when you try to pull them out with a pair of tweezers because the spines are barbed in one direction. These barbs allow the spine to go in smoothly, but when you pull on it the spines stick into your flesh. If you keep pulling the spine will break and remain embedded in your body.

The best way to remove them is with vinegar. Soaking the foot in a vinegar bath dissolves the spines just like the shell of a hard boiled egg dissolves after being left in vinegar for several days. The shell is made of calcium carbonate, and vinegar penetrates it’s structure and basically melts it.

Sea Urchin Stingers

The sea urchin is not aggressive and is found in the sandy crevices, coral reefs, or rocky bottoms of shallow water. Most people do not see them, but when they step on them, they quickly and painfully realize their presence.

Not all sea urchins are venomous, but the pain from stepping on any of them can be intense.

  • Spines
    These create puncture wounds and get stuck in the skin, resulting severe pain, swelling, and redness, that could lead to infection. Typically, there are multiple spines stuck in the foot, commonly over 10, and the more you have the worse you feel.
  • Pedicellarines
     These tiny claws found deep between the spines, that bite onto the skin and   inject venom. They only reach you after you’ve been impaled by the spine deep enough, and the more bites you get the more venom enters your body, causing   symptoms such as muscle aches, weakness, fatigue, and in some cases    respiratory failure, paralysis, and shock resulting in death.

Treatment After Stepping On A Sea Urchin

  • Hot Water Soak for 30 to 90 minutes
    Helps control pain
  • Tweezers
    Tweezers are a big no-no. They will break the spine.
  • Vinegar Soak
    • Kills bacteria
    • Prevents bacterial feasting by the urchin tissues
    • Dissolves the spine
  • Shaving Cream and Razor
     Apply shaving cream and then use a razor to scrape the pedicellarines off.
  • Soap And Water
     Once spines are out, scrub the open wounds with soap and water, using fresh     water to flush the holes.
  • Pain Relief

Advil or Tylenol taken every 6 to 8 hours should control the pain
*Don’t use tape or glue to seal the wound. Leave it open.

Signs Of Infection

  • Redness
  • Pus
  • Hot To Touch

Treating Infection

  • Topical antibiotic ointment
  • Prescription antibiotics

Aviding Stepping On Sea Urchins

  • Be extra careful on shorelines that are rocky or covered in coral
  • Look carefully as you step into and out of the ocean water
  • If you notice an area with a lot of sea urchins, choose another location to enter and exit the ocean water
  • Do not pick them up

Sea Urchin Facts

  • Sea urchins look like a ball covered in porcupine spikes.
  • Found in every ocean on earth
  • 950 species
  • 2 to 3.9 inches in diameter
  • Made up of equal parts.
  • Most are brown, black, red, purple, or green
  • 5 pairs of tubed feet with suckers on the bottom, laid out in rows
  • Some are venomous
  • Their mouths hqve 5 teeth that are so sharp they can make holes in a rock
  • They live approximately 30 years
  • The red sea urchin can live for 200 years when in the wild

Venomous Sea Urchins

  • Venom released into puncture wounds through spines
  • Long spined

-Echinothrix genii

  • Short spined

-Phormosoma genii

  • Shoot venom from tip of spine through bulbous sacs
    • Short Spined


  • Uses Pedicellaria jaws to bite and inject venom
    • Flower

-Toxopneustes pileolus

Did You Step On A Venomous Sea Urchin?

Unless you can identify the above mentioned sea urchin species after stepping on one, you will have to go by your symptoms. Do not pick up the sea urchin or try to take it home to identify it.

Pain is normal, but if the pain becomes too much to handle, accompanied by the following, get to a hospital

  • Shortness of breath
  • Chest pain
  • Weakness


Getting stung by a sea urchin is almost always accidental, either by stepping one one or swimming by on. Their spines are sharp enough to penetrate a diving suit. Most sea urchins are non-venomous and symptoms resolve themselves within 6 hours. A vinegar soak is the best way to remove spines from the body. Do not attempt to remove the spines with tweezers, they will just break. Control pain with Advil or Tylenol, and a hot water soak. Seek medical help for shortness of breath, chest pain, or weakness.


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