[12] Contact with its milky sap (latex) produces bullous dermatitis, acute keratoconjunctivitis and possibly large corneal epithelial defects.

[14] Ingestion can produce severe gastroenteritis with bleeding, shock, and bacterial superinfection, as well as the potential for airway compromise due to edema.

[15] When ingested, the fruit is reportedly "pleasantly sweet" at first, with a subsequent "strange peppery feeling ... gradually progress[ing] to a burning, tearing sensation and tightness of the throat."

Symptoms continue to worsen until the patient can "barely swallow solid food because of the excruciating pain and the feeling of a huge obstructing pharyngeal lump.

"[5] In some parts of its range, many trees carry a warning sign – for example on Curaçao – while others are marked with a red "X" on the trunk to indicate danger.

[16] Although the plant is toxic to many birds and other animals, the black-spined iguana (Ctenosaura similis) is known to eat the fruit and even live among the limbs of the tree.

[12] Spanish explorer Juan Ponce de León died shortly after an injury incurred in battle with the Calusa in Florida—being struck by an arrow that had been poisoned with manchineel sap.

This poison is of such a malignant nature that a single drop of rain or dew that falls from the tree upon your skin will immediately raise a blister.