Heat Syncope

Heat syncope or fainting is a mild form of heat illness that often results from physical exertion when it is hot. It occurs when your body, in an effort to cool itself, causes the blood vessels to dilate to such an extent that blood flow to the brain is reduced. Inadequate fluid replacement, which leads to dehydration, usually contributes greatly to this illness.

Symptoms

Faintness
Dizziness
Headache
Increased pulse rate
Restlessness
Nausea
Vomiting
Brief loss of consciousness

Treatment

Lie or sit down in the shade or a cool area
Elevate the feet
Drink fluids containing salt
Refrain from vigorous activity