The jicama root's flesh will not harm you. The plant, however, contains the toxin rotenone, a very poisonous compound commonly used to poison fish and insects. Besides the flesh of the root, the entire plant contains this toxin, making it unsuitable and dangerous to consume. You should always peel the skin entirely and wash thoroughly to avoid ingesting rotenone. The skin of the root may not have as much toxin in it as the stems and leaves but can still make you very ill if you eat enough.