Fainting is a symptom of a number of metabolic and chronic disorders. If it occurs more than once and is not related to a particular event, such as a scare or lack of food, it is best to seek the advice of a qualified practitioner.
Blood and other chronic deficiencies can contribute to the problem. Use blood tonic and other tonic herbs on a long-term basis. The essential oils of camphor, lavender, or peppermint can be inhaled.

Causes
Fainting may occur while or after you:
Have Thrombocytosis
Cough very hard
Have a bowel movement (especially if you are straining)
Have been standing in one place for too long
Urinate

Other causes of fainting:
Certain medicines, including those used for anxiety, depression, and high blood pressure (these drugs may cause a drop in blood pressure)
Drug or alcohol use
Hyperventilation
Low blood sugar
Seizures
Sudden drop in blood pressure (such as from bleeding or being severely dehydrated)
Standing up very suddenly from a lying position

Natural home remedies
If it's a scorcher of a day and you're feeling every degree of it, or if you're in a very warm room that's making you feel faint, just run cold tap water over the insides of your wrists. If there are ice cubes around, rub them on your wrists. Relief is almost immediate.

A friend of ours is a paramedic. When one of her patients is about to faint, she pinches the patient's philtrum-the fleshy part between the upper lip and nose. That prevents the faint from happening.

If you're prone to fainting spells-a case of the vapors, perhaps-keep pepper handy. Sniff a grain or two and sneeze. The sneeze stimulates the brain's blood vessels and may help prevent fainting. It's good to remember, since not many households have smelling salts, but just about all have black pepper.

Check your eating habits. Are you eating regularly at mealtimes? Are you eating good, wholesome meals with a sufficient amount of protein, and without an excess of sweets and refined foods? Sometimes low blood sugar or a poor diet can cause a person to faint.