A person might experience a drop in blood pressure when they stand up which reduces circulation to the brain causing the person to lose consciousness.
A type of fainting called vasovagal syncope causes the heart beat to slow down or pause for a few seconds causing the person to lose consciousness. This could be due to seeing an unpleasant sight, sudden pain, anxiety, fear, extreme emotional stress or heat.
Fainting can occur due to hyperventilation (inhaling too much oxygen and exhaling too much carbon dioxide quickly). This usually happens when a person is panicking.
A person could faint as a result of their body being dehydrated.
Fainting can happen when a person consumes high amounts of alcohol.
The kind of fainting related to heart problems is called cardiac syncope. People of older age are more at risk of this kind than younger people. This could be due to irregular heart rhythm, for example.
Fainting might happen due to inflammation and pain of a certain nerve found in the mouth.
Fainting may occur after an intense coughing session. This type of fainting is called cough syncope.
Fainting could happen when a person is stretching their arms and neck as a result of stimulating a certain nerve. This type of fainting is called stretch syncope.
A person could experience fainting after or during urination as a result of stimulating a specific nerve. This is called micturition syncope.
A person may faint when they experience a seizure which is accompanied by a number of other symptoms such as feeling of confusion afterward, muscle spasms, drooling or frothing and teeth clenching.
A person might experience fainting when they are having a heart attack.
A person with low blood sugar (hypoglycemia) may experience loss of consciousness. People with diabetes are more likely to experience this type of fainting.
Some people may experience fainting as a result of being allergic to a certain medication. Other symptoms which might accompany loss of consciousness are rash, fever and trouble breathing.
People who have certain food allergies may experience fainting in extreme situations. Fainting is a severe symptom of food allergy that does not always happen.
People with eating disorders such as anorexia nervosa may experience fainting as a result of severe weight loss and their body's deprivation of food.
Fainting can happen as a result of a pulmonary embolism (blood clot in the lung).
Reflex anoxic seizures (RAS) are more common among young children where their hearts involuntarily slow down and may even stop beating for 5-30 seconds. This type of fainting is accompanied with rolled back eyes, crawled fingers and body jerks.