The only difference with the latter is you have to pay for the relief, and it doesn't last much longer. Mentholated aloe vera lotions work better, as do anti-inflammatories such as Motrin or Advil. Heat exhaustion is the most common form of heat illness. It is caused by the depletion of the body's salt or water through exertion. Symptoms include nausea, headache, weakness, confusion, chills, faintness, and rapid pulse.
Victims often have cool, clammy skin.
I once helped resuscitate a victim of heat exhaustion who had collapsed while hunting Hungarian partridge in Montana, which is only notable because the state is not known for high heat, especially in September. You don't have to be in the tropics to suffer. Victims will recover if you get them out of the sun and have them drink lots of fluids. Stave off heat exhaustion by limiting exposure and exertion during the heat of the day and drinking lots of fluids to replace salts lost through sweating. Rest often, and if you must hike during midday, periodically dip your handkerchief or hat into water to get some evaporative cooling underway as you walk.