Heat-related illness includes dehydration, heat cramps, heat exhaustion, heat stroke and worsening of existing medical conditions. If you have a medical condition such as heart disease, diabetes, or kidney disease and if you take certain medications, heat can make your symptoms worse. No matter what heat-related illness, the best way to prevent it is to drink plenty of water and to stay as cool as possible.

Remember the 4 key messages to keep you and others healthy in the heat

1. Keep yourself cool, 2.Stay hydrated with water, 3. Lookout for each other, 4. Plean ahead for the heat 


Mild to moderate dehydration makes the heart work faster and leads to reduced fluid available for sweating.


  • Dizziness
  • Tiredness
  • Irritability
  • Thirst
  • Bright or dark yellow urine*
  • Loss of appetite
  • Fainting

*see urine colour chart

What to do - first aid

  • Drink plenty of water or diluted fruit juice (1 part juice in 4 parts water); avoid tea, coffee or alcohol
  • Move somewhere cool, ideally somewhere air-conditioned
  • If possible use a spray bottle with water in it to cool yourself down
  • If you start to feel unwell, seek medical advice

Heat cramps

Heat cramps usually affect people who sweat a lot during strenuous activity such as sport or gardening in hot weather. The sweating causes the body to lose salt and water. The low salt level in the muscles may be the cause of heat cramps. Heat cramps may also be a symptom of heat exhaustion.


  • Muscle pains or spasms​

What to do - first aid

  • Stop all activity and lie in a cool place, legs slightly raised
  • Drink water or diluted fruit juice (1 part juice in 4 parts water)
  • Have a cool shower or bath
  • Massage your limbs to ease spasms, apply cool packs
  • Do not return to strenuous activity for a few hours after the cramps subside (exertion may lead to heat exhaustion/ heat stroke)
  • Seek medical advice if there is no improvement

Heat exhaustion

Heat exhaustion is the body’s response to an excessive loss of water and salt contained in sweat. Those most at risk of developing heat exhaustion are elderly people, people with chronic diseases, and people working or exercising in a hot environment. If heat exhaustion is not treated, it can turn into heat stroke.


  • Heavy sweating (cool and moist skin)
  • Pale skin
  • Fast and weak pulse rate
  • Breathing fast and shallow
  • Muscle weakness or cramps
  • Tiredness
  • Dizziness
  • Headache
  • Nausea or vomiting
  • Fainting​

What to do - first aid

  • Move to a cool place, if possible in an air-conditioned room and lie down
  • Remove excess clothing
  • Take small sips of cool fluids
  • Cool shower, bath or sponge bath
  • Put cool packs under armpits, on the groin, or on the back of the neck to reduce body heat
  • If symptoms worsen or if there is no improvement, seek urgent medical advice and call an ambulance if necessary

Heat stroke

In a person with heat stroke, the body temperature is not controlled properly. It occurs when the body temperature rises above 40.5°C. Heat stroke is a life-threatening emergency. Immediate first aid is very important and the aim is to lower body temperature as quickly as possible.


  • A sudden rise in body temperature
  • Red, hot and dry skin (sweating has stopped)
  • Dry swollen tongue
  • Rapid pulse
  • Rapid shallow breathing
  • Intense thirst
  • Headache
  • Nausea or vomiting
  • Dizziness
  • Confusion, poor coordination or slurred speech
  • Aggressive or bizarre behaviour
  • Loss of consciousness
  • Seizures or coma

What to do - first aid

  • Immediately call 000 and ask for an ambulance
  • Get the person into the shade, lay them down, and keep them as still as possible
  • Give small sips of cool fluids if conscious and able to drink
  • Bring their temperature down using any method available (sponging with cool water, cool shower, spraying with cool water from the garden hose or soaking clothes with cool water)
  • Put cool packs under armpits, on the groin, or on the back of the neck to reduce body heat
  • Do not give aspirin or paracetamol; they do not help and may be harmful
  • If unconscious, lay the person on their side (recovery position) and check they can breathe properly
  • Perform CPR if needed
Page Updated: Friday 2 December 2016
Contact page owner: Environmental Health