Heat Exhaustion is a form of shock principally triggered in gardeners by a combination of dehydration and sustained gardening activity. It manifests as heavy sweating or clammy skin sometimes with body/core temperature near normal but the feeling of not quite right.

Heat exhaustion can also occur without heavy activity when the core temperature (the temperature inside the body) rises above the normal 37°C (98.6°F) towards 38-39°C (100-102°F) or higher.

Pupils may dilate (widen), headache and nausea may arise leading to dizziness and potentially vomiting.  It can reverse upon following first response advice but it can be serious and develop further into a major medical incident.

First response: Retire casualty to a cooler location (shade of a tree or interior with air conditioning). Remove some layers of clothing if overdressed.  Direct cooling air onto the casualty with a fan or improvised fan (newspaper). It is ok to sip cool but not ice cold water. 

An isotonic drink would be helpful but not any energy drinks or caffeinated beverages. A spritz of cool water on face and exposed skin is beneficial. A damp towel or cool compress for the head, neck or face is relieving and reassuring.

Generally these methods should make the casualty feel much better within fifteen minutes to half an hour and without any further long-term complications but if no improvement seems to be happening then place the casualty in the shock position (lying flat on their back with feet raised) call an ambulance and continue to fan.

Without treatment or abatement upon first aid, heat exhaustion could easily develop into heatstroke.

Heatstroke is a much more serious condition than heat exhaustion. It occurs in a gardening context when heavy work on hot days combined with inadequate rest breaks and insufficient fluid intake – forcing the body into a stress reaction where it can no longer sweat or cool itself and so keeps on overheating.

With heatstroke core temperature can elevate above 40°C (104°F) at which point the cells inside the body start to break down and internal organs can commence to shut down. 

The symptoms of heatstroke can include a mixture of the following- hot and bothered, elevated body temperature, rapid heartbeat, rapid and shallow breathing, feeling dizzy, mental confusion, headache, nausea, cessation of sweating, loss of consciousness. Untreated it can lead to organ failure, coma, brain damage and death.

A key diagnostic is that heat stroke can cause pupils to shrink small – become pinned. Help cool and calm/focus the casualty. Medical assistance will be required.

First response: Heatstroke is a medical emergency and should be treated immediately. Call for help and dial emergency services to request an ambulance.

While awaiting ambulance- move casualty to a cool location (shade of a tree or indoors to air-conditioned room). Remove layers of clothing if overdressed.  Direct cooling air onto the casualty with a fan or improvised fan (newspaper).

It is ok to sip cool but not ice cold water.  A spritz of cool water on face and exposed skin is beneficial. Wrapping in a cool damp bed sheet will help to cool quickly but not too rapidly to cause additional stresses/complications.

If casualty starts to have a seizure (fit), move nearby objects out of their way to prevent further injury. Post-fit or if the person becomes unconscious or commences vomiting, move them into the recovery position and keep airway clear. Continue to fan until ambulance arrives.