Prevention of heat illnesses

This article was contributed by the Department of Health.

Under very hot weather in the summer days, members of the public, particularly those undertaking outdoor activities, should take necessary measures to prevent heatstroke and sunburn.

The public should carry and drink plenty of water against dehydration while engaging in outdoor activities. Those who would be engaged in strenuous outdoor activities should avoid beverages containing caffeine, such as coffee and tea, as well as alcohol, as they speed up water loss from the body through the urinary system.

Children, the elderly, the sick (including those with heart disease or high blood pressure) and obese persons, who are more vulnerable to heat-related illnesses, should pay special attention.

The public should adopt the following preventive measures when going outdoors under very hot weather:

  • Wear loose and light-coloured clothing to reduce heat absorption and facilitate sweat evaporation and heat dissipation;
  • Avoid vigorous exercise and prolonged activities like hiking or trekking as heat, sweating and exhaustion can place additional demands on the physique;
  • Perform outdoor activities in the morning or late afternoon;
  • For indoor activities, open all windows, use a fan or use air-conditioning to maintain good ventilation; and
  • Reschedule work to cooler times of the day.

If working in a very hot environment is inevitable, introduce shade in the workplace where practicable, and start work slowly and pick up the pace gradually. Get into a cool area for rest at regular intervals to allow the body to recuperate.

The public should also note the latest and the forecast Ultraviolet (UV) Index released by the Hong Kong Observatory (HKO). When the UV Index is high (6 or above):

  • Minimise direct exposure of the skin and the eyes to sunlight;
  • Wear long-sleeved and loose-fitting clothes;
  • Wear a wide-brimmed hat or use an umbrella;
  • Seek a shaded area or put on UV-blocking sunglasses; and
  • Apply a broad-spectrum sunscreen lotion with a Sun Protection Factor (SPF) of 15 or above. Apply liberally and reapply after swimming, sweating or toweling off.

If symptoms (such as dizziness, headache, nausea, shortness of breath or confusion) develop, rest and seek medical advice as soon as possible.

For further information on the prevention of heat stroke and protection against UV radiation, the public may call the Health Education Infoline of the Department of Health on 2833 0111 or visit the website of the Centre for Health Protection (

The public may also call ‘Dial-a-Weather’ on 1878 200 or visit the HKO’s website ( for the latest weather information and forecast.