Cardiologist Hugo Café explains what thermal shock is, the situations of greatest risk, and—above all—how to prevent it.
Read carefully and share this information with your family and friends.
What is thermal shock?
Thermal shock is an extreme bodily reaction to a sudden change in temperature. For example, when entering cold water abruptly after long exposure to intense sun and heat.
It may cause:
- Difficulty breathing;
- Irregular heart rhythm (arrhythmias);
- Fainting or loss of consciousness;
- In severe cases, cardiorespiratory arrest;
- This phenomenon can happen to anyone, even healthy individuals.
High-risk situations:
- Spending a long time in the sun, causing the body to overheat;
- Diving suddenly into cold water;
- Exercising on the beach followed by an immediate swim;
- Ignoring warning signs such as dizziness or heart palpitations.
How to prevent thermal shock:
- Cool down before entering the sea
Use a shower or wet yourself gradually: start with your feet and legs, then your torso and arms, and finally your head.
- Avoid sudden dives
Enter the water slowly and calmly so your body can adjust to the temperature.
- Don’t go into the water immediately after sun exposure
Rest for a few minutes in the shade before going into the sea.
- Stay well hydrated
Drink water regularly. Dehydration worsens the effects of heat.
- Pay attention to your body
If you feel dizzy, nauseous, short of breath or have palpitations, do not enter the water.
- Never swim alone
Whenever possible, swim with someone and near lifeguards.
In case of emergency:
- Call 112 immediately
- Remove the person from the water safely
- If trained, start CPR (Basic Life Support)
Protect yourself and others.
A simple precaution can save lives.
Dr. Hugo de Mendonça Café
Cardiologist HPA
OM: 47617
24, July 2025
