Why aren't onions recommended for everyone? These are the risks of eating them.

Onion is one of the most widely used ingredients in cooking around the world. Whether raw, cooked, caramelized, or in sauces, it provides flavor, texture, and antioxidant properties . However, although it is recognized for its benefits, not everyone tolerates it equally , and its consumption can cause side effects in some cases.

Knowing the potential risks of eating onions is key to avoiding discomfort and maintaining digestive health. Here, we explain when and why this popular vegetable may not be suitable for everyone.

One of the most common side effects of onions is their potential to cause digestive upset . This is because they contain fructans , a type of fermentable carbohydrate that can cause:

• Abdominal swelling
• Excessive gas
• Cramps
• Diarrhea or constipation

People who suffer from irritable bowel syndrome (IBS) or FODMAP sensitivity are especially vulnerable to these symptoms. In these cases, even small amounts of onion—raw or cooked—can trigger significant discomfort.

Another group that should be cautious with onions is those who suffer from gastroesophageal reflux disease (GERD) . Studies have shown that onions, especially raw, relax the lower esophageal sphincter , making it easier for acid to return to the esophagus.

This can lead to:

• Persistent heartburn
• Burning sensation in the chest
• Frequent belching
• Discomfort when sleeping after dinner

Reducing or eliminating raw onions from your diet can help alleviate these symptoms, especially if consumed at night.

Although uncommon, some people may have an allergy or intolerance to onions . Symptoms can range from mild to severe, and include:

• Itching or swelling in the mouth
• Hives or skin rashes
• Difficulty breathing (in extreme cases)
• Abdominal pain and vomiting

These types of reactions are usually related to the proteins in the vegetable and not to its cooking, so even cooked onions can cause symptoms in people with allergies.

Onions contain natural compounds that may have a mild blood-thinning effect . This generally doesn't pose a risk for most people, but it may be important for those taking blood-thinning medications (such as warfarin).

In these cases, excessive onion consumption could increase the risk of bleeding , especially when combined with other foods with similar properties, such as garlic, ginger, or ginkgo biloba.

It is always advisable to consult your doctor if you are taking this type of medication and consume onions regularly.

Some research has suggested that, in excess, the sulfur compounds in onions may stimulate immune responses in people with autoimmune diseases . Although more evidence is needed, caution is advised if you have conditions such as:

• Lupus
• Rheumatoid arthritis
• Hashimoto's thyroiditis

Similarly, migraine sufferers also report that onions, especially when raw, can act as a headache trigger .

Not necessarily. Onions are still a healthy food, rich in antioxidants, vitamin C, and anti-inflammatory compounds . The problem isn't their presence, but rather how each body reacts to them.

If you don't experience discomfort when eating it, there's no reason to eliminate it from your diet. But if you notice digestive symptoms, frequent heartburn, or any type of intolerance, consider:

• Reduce your consumption , especially in its raw form
• Opt for milder varieties such as cooked white onion
• Consult a specialist if symptoms persist.

Onions are a vegetable packed with benefits, but not everyone tolerates them well. Whether or not they belong in your diet depends on your health conditions, your digestive system, and your medical history . As with many foods, moderate consumption, personal observation, and professional advice can make the difference between a healthy food and a constant source of discomfort.