06/10/2025
The black marks or spots you sometimes see on onions are usually caused by a fungal infection, most commonly black mold — caused by the fungus Aspergillus niger.
Here’s what you should know 👇
🔍 What It Looks Like
Black or dark gray powdery patches, often around the neck, roots, or between onion scales.
Sometimes, the onion looks normal on the outside but has black dust-like spores inside when peeled.
⚠️ Health Risk
Yes, it can be dangerous, especially if consumed in large quantities or by people with weakened immune systems, asthma, or allergies.
The fungus can produce mycotoxins that may cause:
Respiratory irritation when inhaled
Allergic reactions
Gastrointestinal issues if eaten
✅ What to Do
If the black mold is superficial (on the dry outer skin only), you can peel off several layers until the onion looks clean and firm.
If the mold has penetrated inside or the onion feels soft, slimy, or smells bad, discard it immediately.
Always store onions in a cool, dry, well-ventilated place to prevent mold growth.
