Seems like undecenoic acid is not without side effects. This may depend on the sensitivity of the individual/dosage. Myself has experienced dizziness and some GI distress with it. Seems like at times it can affect mood/nervous system as well.
Special Remarks on other Toxic Effects on Humans:
Acute Potential Health Effects: Skin: Causes skin irritation. It may be absorbed through the skin. It may be slightly hazardous
if absorbed through the skin. Eyes: Causes eye irritation. Inhalation: May cause respiratory tract irritation. Ingestion: Ingestion
of large amounts may cause gastrointestinal disturbances, and may affect behavior/central nervous system (excitement,
somnolence, muscle contraction or spasticity, headache, dizziness), and metabolism (loss of appetite). Chronic Potential
Health Effects: Prolonged or repeated ingestion may cause weight loss or anorexia.