Sand dollars are flattened sea urchins belonging to the class Echinoidea, making them relatives of starfish and sea cucumbers. They are often found washed ashore, but questions regarding their safety arise when beachgoers encounter them alive. While they do not pose a serious biological threat, understanding their physical characteristics is important for safe beach interaction.
The Hazards of Live Sand Dollars
When a sand dollar is alive, it appears dark—typically green, brown, or purple—and is covered in a dense layer of short, fine spines. These spines are not the long, sharp structures found on some true sea urchins; they are velvety and hair-like, used for movement, burrowing, and feeding on the sandy seafloor. They also assist in gas exchange and gathering food particles.
Despite their soft appearance, these calcium carbonate spines can cause minor physical injury if encountered with force. Stepping on a live sand dollar or handling one roughly may result in small puncture wounds or skin irritation. These injuries are usually minor, but any break in the skin carries a risk of infection from marine bacteria. When stressed, a live sand dollar may also release a yellow-orange substance called echinochrome, which is harmless to humans but can temporarily stain the skin.
Physical Risks from Found Shells
The familiar white, circular item found scattered on beaches is the sand dollar’s skeleton, known as the “test.” Once the animal dies, the soft tissue decays, the sun bleaches this rigid structure, and the spines fall off, leaving behind a smooth, brittle object. This brittle nature poses the primary physical risk to beachgoers.
The dried test is thin and composed of calcium carbonate plates, making it prone to breaking into sharp fragments. If a person steps on a broken piece, the edges can cause lacerations or deep cuts to the foot. Carelessly handling a fragmented shell can also result in splinters or embedded debris in the hand. The danger from the dead shell is purely mechanical, centered on the risk of cuts from its sharp, delicate edges.
Are Sand Dollars Venomous or Toxic
Sand dollars are not venomous and do not produce toxins harmful to humans. Unlike some relatives in the echinoderm phylum, such as certain sea urchins that possess venom-injecting structures, sand dollars lack any mechanism to deliver poison. Their defense strategy relies mainly on burrowing quickly into the sand to hide from predators.
The yellow-orange substance they may release when alive, echinochrome, is a harmless chemical compound. Therefore, the concern that a sand dollar could deliver a painful sting or inject a toxin is unfounded.
Safe Interactions and Prevention
Beachgoers can prevent minor injuries by adopting a few simple precautions when in shallow, sandy waters. Wearing protective footwear, such as water shoes or sandals, shields the feet from potential puncture wounds from live sand dollars buried beneath the surface. It is also recommended to shuffle the feet when wading, which gives any buried organism time to move away.
If a live sand dollar is encountered, it is best practice to leave it undisturbed or gently return it to the water, as they cannot survive long out of their habitat. For those collecting the dead, white tests, inspect the shells carefully for sharp or broken edges before picking them up. If a minor cut or scrape occurs from a shell fragment or a spine, clean the wound immediately with fresh water and soap to minimize the risk of infection. If a spine fragment remains embedded or signs of infection appear, seeking medical attention is prudent.