Heatstroke: symptoms, what to do and how to protect your skin in summer
A guide for the Brazilian summer: how to recognise heatstroke, tell it apart from heat exhaustion and sunburn, understand sun allergy and stay protected on the beach, at parties and on end-of-year trips.
Heatstroke is the overheating of the body after a long time in strong sun and intense heat: the temperature rises above 40 °C, sweating fails and the body cannot cool itself. The first signs are headache, dizziness, nausea, hot and dry skin and a fast pulse. Some signs mean an emergency: see the alert in the symptoms section. In December, with the beach, parties and travel, sunburn and sun allergy reactions also become more common. This guide shows how to recognise each condition, what to do and how to prevent it.
Understanding the condition
Heatstroke: what it is and why it happens in summer
Heatstroke happens when heat overwhelms the body's ability to cool itself.
According to the Ministry of Health, heatstroke is caused by too much exposure to the sun and intense heat. It occurs when body temperature rises above 40 °C, the sweating mechanism fails and the body can no longer lose heat. It is more common in hot, dry weather, but it can also happen in humid places, such as the coast in summer.
As the temperature rises quickly, the body loses a lot of water and mineral salts. For this reason, heatstroke can come together with dehydration.
A review published in the Revista Brasileira de Medicina de Família e Comunidade describes heat stress as a condition that starts with non-specific symptoms, such as feeling unwell, headache and nausea. Heat exhaustion, if left untreated, can progress to heatstroke, a serious illness that affects the central nervous system.
Sources: Ministry of Health, Technical Note No. 38/2023; Floss and Barros, RBMFC 2020.
Recognising the signs
Heatstroke symptoms: from the first signs to severe ones
Symptoms start mild and get worse the longer the exposure lasts.
First symptoms
- Headache and dizziness
- Nausea
- Hot, dry skin
- Fast pulse
- High temperature
- Changes in vision
In older people, excessive heat can also cause heavy sweating, pale, cold and clammy skin, cramps, tiredness and a fast, weak pulse.
Do not mix them up
Heatstroke, heat exhaustion and sunburn: what is the difference
In everyday speech, “insolação” is used for several summer problems. They differ in seriousness.
| Condition | What happens | Typical signs |
|---|---|---|
| Heat exhaustion | The body is overloaded by heat but can still cool itself | Feeling unwell, headache, nausea, tiredness, heavy sweating |
| Heatstroke | The temperature rises above 40 °C and sweating fails | Hot, dry skin, fast pulse, dizziness, confusion |
| Sunburn | Ultraviolet radiation damages the skin | Redness, burning, pain when touched and sometimes blisters |
| Sun allergy | The skin reacts excessively to light | Itching, redness and small blisters on exposed areas |
The conditions can appear together. A whole day at the beach without protection can cause sunburn and heat exhaustion at the same time.
Sources: Ministry of Health, Technical Note No. 38/2023; Floss and Barros, RBMFC 2020; SBD, Photosensitivity.
Extra care
Who is at higher risk in the December heat
Anyone can get heatstroke, but some groups dehydrate and overheat faster.
The Ministry of Health lists the following as risk factors for heat-related illness:
- Age: children and older people
- Drinking too little fluid
- Too much alcohol or caffeine
- Gastroenteritis, with vomiting or diarrhoea
- Taking some medicines, such as antihypertensives, diuretics, antidepressants or antipsychotics
- Chronic conditions, such as heart, kidney and respiratory problems
In children, the younger they are, the more vulnerable. In older people, the body holds less water, the sense of thirst fades and temperature regulation works less well. If you are hosting parents or grandparents over the end-of-year holidays, offer water often, even if they say they are not thirsty.
Do not stop regular medicines on your own because of the heat. If you take a diuretic or blood pressure medicine and will spend days at the beach, talk to a doctor first.
First aid
What to do in case of heatstroke
The aim is to cool the body and replace fluids as soon as possible.
- Get out of the sun and move to a cool, ventilated place or one with air conditioning
- Remove excess clothing and prefer light, loose clothes
- Place damp cloths with cool water on the wrists, face and back of the neck
- Give fluids in small amounts if the person is awake and able to swallow: water, coconut water, juice or oral rehydration solution
- Avoid alcohol and caffeine until fully recovered
- Watch how things develop over the following hours, especially in children and older people
Mild cases without warning signs usually improve with rest, shade and hydration. If the headache, nausea or tiredness continue the next day, a medical assessment is worthwhile.
Sources: Ministry of Health, Technical Note No. 38/2023; Floss and Barros, RBMFC 2020.
Caring for the skin
Sunburn: how to care for your skin after the beach
Sunburn is skin damage caused by ultraviolet radiation, not just a tan that went too far.
The skin turns red, hot and sore. In stronger burns, blisters appear. A few measures help recovery:
- A cool or lukewarm shower, never hot
- Moisturiser every day on the affected skin
- More fluids: water, fruit juices and coconut water
- No more sun on the burned area until the skin has recovered
- Do not pop the blisters
Seek medical assessment if the burn has blisters over a large area, comes with fever or chills, or affects a baby or a small child. A widespread burn can come together with heat exhaustion or heatstroke.
Source: SBD, Skin care in summer.
Photosensitivity
Sun allergy: photosensitivity and lime marks
“Sun allergy” is the popular name for skin reactions that appear with sunlight, known as photosensitivity.
According to the Brazilian Society of Dermatology (SBD), photosensitivity is an uncommon reaction of extreme skin sensitivity to light. It has two main types:
- Phototoxic: the most common. It appears minutes or hours after sun exposure and stays limited to the exposed area.
- Photoallergic: rarer. It involves the immune system, usually appears one to three days later and can spread beyond the exposed area.
The most common symptoms are itching, redness, patches and small blisters. Plants, perfumes, cosmetics and some antibiotics can trigger the reaction when combined with sun.
Lime marks
A typical case in the Brazilian summer is phytophotodermatitis. Citrus fruits such as lemon, lime and tangerine contain substances called furocoumarins. If the juice gets on the skin, for example when making a caipirinha at the beach, and the sun follows, red marks appear, often in lines or splashes, sometimes with blisters. They show up between 24 and 48 hours later. To prevent this, wash the skin well with running water and mild soap right after contact.
Treatment of sun allergy depends on the type of reaction and is prescribed by a doctor. If you had a reaction after starting a new medicine, mention this at the consultation.
Sources: SBD, Photosensitivity; SBD, Phytophotodermatitis.
Before you go out
How to prevent heatstroke and sunburn: sunscreen and timing
Prevention combines three things: shade at peak hours, skin protection and plenty of water.
- Sunscreen with SPF 30 or higher, with protection against UVA and UVB rays
- Apply 30 minutes before going out in the sun, over the whole body, including hands, ears, nape and feet
- Reapply every two hours, and sooner if you sweat a lot or get in the water
- Avoid the sun between 10h and 16h, as the SBD recommends
- Wear a hat, cotton clothing and sunglasses; synthetic fabrics such as nylon block only about 30% of the radiation
- Prefer cotton or canvas beach tents at the beach
The Ministry of Health advises avoiding physical activity at the hours of strongest sun, especially between 10h and 15h. Running along the seafront, footvolley and long walks are best left for early morning or late afternoon.
Black skin also needs protection. It has more natural protection, but it is not immune to burning or to sun damage.
Sources: SBD, Skin care in summer; Ministry of Health, Technical Note No. 38/2023.
End of the year
Beach, parties and end-of-year travel without heatstroke
December brings strong sun, alcohol, long journeys and a routine out of the ordinary. This combination favours heatstroke.
- Alcohol and caffeine: the Ministry of Health advises avoiding them in intense heat. If you do drink, alternate each drink with water.
- Children: sunscreen can be used from six months of age. Younger babies should stay in the shade.
- Car journeys: never leave children, older people or animals inside a parked car in the sun.
- Older relatives: keep the house ventilated, offer water and watch for confusion or unusual tiredness.
- Light meals: choose healthy foods and drink more on the hottest days.
If gastroenteritis appears in the middle of a trip, the risk of dehydration in the heat goes up. In that case, increase fluids from the first episode of vomiting or diarrhoea.
Sources: Ministry of Health, Technical Note No. 38/2023; SBD, Skin care in summer.
In the long term
Repeated sunburn and the risk of skin cancer
A sunburn goes away in a few days, but the damage to the skin's DNA builds up.
According to the SBD, skin cancer accounts for 33% of all cancer diagnoses in Brazil. Having had sunburn and finding it hard to tan are among the factors that raise the risk. The SBD recommends keeping babies and children protected from the sun, using sunscreen every day, even on cloudy days, and reapplying it every two hours during outdoor activities.
Keep an eye on your skin. A mole that changes colour, size or shape, or a sore that does not heal, deserves medical assessment.
Source: SBD, Skin cancer.
Online care
Online clinical consultation for heatstroke and summer skin problems
Without emergency signs, a video conversation with a doctor helps you understand what is happening and decide the next step.
In the Online Clinical Consultation, you speak by video with a doctor with an active CRM registration. Care is usually available on the same day in most cases. For heatstroke, sunburn or sun allergy, the doctor:
- Assesses the symptoms: how long you were in the sun, what you drank, the medicines you take and how you are now
- Looks at the skin by video, helping to tell apart sunburn, sun allergy and other lesions
- Advises on hydration and care for the coming days
- Looks for warning signs and directs you to urgent care when they appear
- Issues a digital treatment plan, a request for tests or a referral to a private specialist, when clinically indicated
- Assesses the need for a medical certificate if you have to take time off work; the consultation does not guarantee that a certificate will be issued or accepted
- Schedules a follow-up to monitor progress, if necessary
An online consultation does not replace an in-person examination. When you need to be examined in person, the doctor will say so clearly and advise you where and how to do it.
Next step
Continue with the right care
If there are no emergency signs, an online clinical consultation helps assess the situation, guide your care and decide whether an in-person examination is needed.
Felt unwell after a day in the sun?
In an online clinical consultation, the doctor assesses your symptoms, checks for warning signs and advises on skin care and hydration.
References
Sources consulted
Sources checked on 8 November 2026.
The article summarises guidance from the Ministry of Health, the Brazilian Society of Dermatology and a peer-reviewed Brazilian clinical review. The text does not recommend medicines or doses and does not replace medical assessment.
Questions
Frequently asked questions about heatstroke
Does heatstroke cause a fever?
Heatstroke raises the body temperature above 40 °C, but it is not a fever caused by infection: it is the body failing to lose heat. For this reason, the first step is to cool the person, with shade, a cool place and damp cloths.
What is the difference between heatstroke and sunburn?
Sunburn affects the skin: redness, burning and sometimes blisters. Heatstroke affects the whole body: headache, dizziness, nausea, hot and dry skin and, in severe cases, confusion. Both can happen together after a whole day at the beach.
When does heatstroke need urgent care?
The signs of severity are in the alert in the symptoms section. If any of them appear, follow that alert and do not wait for a teleconsultation.
Can children use sunscreen?
According to the SBD, sunscreen can be used from six months of age, preferably with physical filters. Younger babies should stay in the shade, in light clothing and a hat.
Is there treatment for sun allergy?
Yes. Treatment depends on the type of reaction and is prescribed by a doctor. The basis of prevention is protecting the skin from the sun and avoiding contact with substances that cause the reaction, such as lime juice before going out in the sun.
