What causes some people to faint all of a sudden?

Fainting, also referred to as Syncope, occurs when you suddenly lose consciousness, due to a drop in your blood pressure or when your brain fails to get sufficient amounts of oxygen. While the cause of fainting often tends to be minor, it can also be an indication of an underlying illness.

Individuals who pass out generally suffer from the fainting spell for about a few seconds to a few minutes. Often, there’s a feeling of dizziness, weakness, lightheadedness, and nauseousness before you faint. Some people also experience blacking or whiting out, where the sense of hearing and sight fades away before eventually fainting.

Fainting generally isn’t much of a concern and recovery happens within a few minutes. However, if you experience numerous instances of fainting in the past few weeks or months, seek immediate medical attention as it can be a symptom of a severe medical condition.

While it is somewhat scary, syncope is actually a survival mechanism of the body when oxygen supply to the brain suddenly drops. When the body detects that blood and oxygen levels are falling, it will begin to switch off non-key parts of the body and allocate remaining resources to the vital organs. That’s why fainting usually happens when there are issues with blood circulation, breathing or if someone suffers from carbon monoxide poisoning.

However, in most cases, the exact cause of fainting remains to be obscure. Yet, numerous factors can trigger a person to pass out, such as:

  • immense pain
  • dehydration
  • a sudden decrease in blood pressure levels
  • hyperventilation
  • exhaustion under hot and temperatures
  • forceful coughing
  • standing too long or getting up too quickly
  • consuming medications and alcohol
  • seizures

In a medical standpoint, there are different types of fainting or syncope. Three of the most common types are as follows:

Situational syncope: This type of fainting happens because of straining during functions, such as urinating, defecating, or coughing.

Vasovagal syncope: Vasovagal syncope is typically triggered by seeing blood, suffering from emotional trauma or stress, or prolonged standing.

Carotid sinus syncope: This type of syncope occurs when the carotid sinus located in the neck gets constricted, causing impaired blood and oxygen to the brain. It can occur due to sudden turns of the head to one side or wearing collars or neck garments that are too tight.

So, what to do when to prevent fainting? First, your doctor should rule out possible causes. If it is traced to be due to an underlying illness, it must be treated to avoid any future passing out episodes.


If it is due to some triggers, then you do your best to steer away from those factors. Make sure to stay hydrated, take time when standing up, and avoid working out or doing vigorous activities in hot and humid environments.

What if someone else faints instead? The initial thing to do is boost blood and oxygen flow to the brain by elevating the feet above the level of the heart. Then, check tight collars, clothes or garments, and accessories, and loosen then up if necessary. If possible, find a cool, calm area where they can recover. Once they gain consciousness, a glass of cold water can also help.

However, if the person also experiences other symptoms, such as numbness on different parts of the body, weakness, paralysis, blurred vision, and slurred speech, they require emergency medical assistance. Pregnant women, diabetic people, and individuals with a history of heart disease, and recurrent fainting must be brought the nearest hospital right away after an episode.

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