Are echinoderms dangerous to humans?

No, echinoderms are life threatening to humans.  However, the spines of echinoderms can cause a nasty sting if touched and these spines generally break off and remain stuck in the skin.  If an individual does come into contact with the spines of an echinoderm, then it is important to remove the spine, which will require a lot of patience and may require the help of a physician.  If a sting has occurred, then there will likely be itching, redness, swelling, and irritation in the area of the sting and a topical hydrocortisone cream can be used if necessary.