That looks like a clickbait headline: “Doctors reveal that eating onion causes … See more”.

Without the rest of the article, there’s no way to know what claim is being made. Many such posts exaggerate health effects to get clicks.

What is actually known about onions?

• Onions contain fiber, antioxidants, and compounds such as flavonoids.
• They may support heart health and provide some anti-inflammatory benefits.
• Eating onions can cause bad breath, heartburn, acid reflux symptoms, gas, or digestive discomfort in some people.
• Some people are allergic or sensitive to onions.

If you can paste the full headline or article text, I can help evaluate whether the claim is accurate or misleading.