Fainting is a temporary loss of consciousness. It happens when there isn't enough blood going to the brain because of a drop in blood pressure.
Why Do People Faint?
Blood pressure can drop from dehydration, a quick change in position, standing or sitting still for a long period, or a sudden fear of something.
Common reasons for fainting include:
Physical triggers. Getting too hot or being in a crowded, poorly ventilated setting are common causes of fainting. Sometimes just standing for a very long time or getting up too fast after sitting or lying down can cause someone to faint.
Emotional stress. Emotions like fright, pain, anxiety, or shock can cause blood pressure to drop. This is the reason why people faint when something frightens them, like the sight of blood.
Hyperventilation. A person who is hyperventilating is taking fast breaths. Carbon dioxide (CO2) levels in the blood fall, causing blood vessels to narrow. Blood flow to the brain decreases, making a person faint.
Pregnancy. During pregnancy, the body undergoes a lot of changes, including changes in the circulatory system. These may cause a woman to faint. And as the uterus grows, it can press on and partially block blood flow through large blood vessels, which can decrease blood supply to the brain.
What Are the Warning Signs of Fainting?
Someone who is about to faint might:
have vision changes
have a fast or irregular heartbeat
sweat a lot
have nausea and/or vomiting
Can Fainting Be Prevented?
If a person feels like they're going to faint, taking these steps might help stop it:
If possible, lie down. This can help prevent a fainting episode, as it lets blood get to the brain. They should stand up again slowly when they feel better. Move to a sitting position for several minutes first, then to standing.
Sit down with their head lowered forward between their knees. This also helps blood get to the brain, though it's not as good as lying down. When they feel better, they can move slowly into an upright seated position, then stand.
Don't get dehydrated. Drink enough liquids throughout the day. Drink plenty of fluids before, during, and after exercise and in hot weather.
Keep blood circulating. People who stand or sit for a long time should take breaks often and move around. Regularly tensing the leg muscles or crossing the legs can help improve blood flow.
Avoid overheated, cramped, or stuffy environments, when possible.
When Should I Call the Doctor?
Usually, there's no need to worry if your child or teen fainted:
it was brief
the reasons why are obvious (like being in a hot, crowded setting)
But if your child has a medical condition or is taking prescription medicines, it's a good idea to call the doctor.
Call the doctor or get medical care if your child or teen:
hurt themselves when they fainted (for example, hit their head really hard)
has chest pain, palpitations (fast or irregular heartbeats), or shortness of breath
had a seizure
fainted during exercise or other physical activity
has fainted more than once
The doctor will ask a few questions, do an exam, and might order some tests, such as:
If your child or teen faints, help them lie down. Don't move them if they're injured from falling (that can make things worse). Instead, loosen any tight clothing, such as belts, collars, or ties. Propping their feet and lower legs up on a backpack or jacket also can help blood flow to the brain.
Someone who has fainted will usually recover quickly. Because it's normal to feel a bit weak after fainting, be sure your child lies down for a bit. Getting up too soon may bring on another fainting spell.
Call 911 if someone who has fainted:
is still unconscious after a few minutes
passed out while exercising
is having chest pain, trouble breathing, or a seizure