Black spots on onions: Kidney damage risk from hidden toxin.

• Onions with black spots should be avoided as they may contain harmful toxins.
• Black spots are caused by *Aspergillus niger* fungus, which can produce ochratoxin A, a toxin known to damage kidneys and liver.
• If an onion has black spots, remove and discard the affected layers; the entire onion does not need to be thrown away.
• Store onions in a dark, cool, well-ventilated place, away from potatoes, to ensure long-term use.

Why It Matters: Black-spotted onions may contain toxins that can damage your kidneys and liver.