5 Conditions Triggered by Excess Sun Exposure

The Problem With Getting Too Much Sun

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Most people like to spend time outdoors on sunny days, but too much sun exposure can have serious consequences, including:

  • Sunburn
  • Dehydration
  • Hyponatremia
  • Heat exhaustion
  • Heatstroke
Woman with sunburnt back


Sunburn is a common skin injury caused by excessive exposure to ultraviolet (UV) radiation from the sun. The injury is triggered by an inflammatory response as UV radiation directly damages DNA in skin cells.

When a cell's DNA is irreparably damaged, it will undergo apoptosis (cell death) and be quickly shed, leading to the peeling and flaking of skin.

Sunburn Symptoms

Common symptoms of sunburn include:

  • Reddish skin
  • Pain
  • Swelling
  • Fatigue
  • Hot skin temperatures
sunburn on arm

DermNet / CC BY-NC-ND

In more severe cases, you may also have:

  • Rash
  • Nausea
  • Fever
  • Dizziness
  • Chills

Contact a medical professional if these symptoms occur.

Second-degree sunburns can manifest with:

  • Blistering
  • Oozing
  • Dehydration
  • Edema (tissue swelling)
  • Fainting

When You're at Risk

Sunburn can begin after only 15 minutes of direct sun exposure. Pain and redness tend to be greatest during the first six to 48 hours.

Sunburns don't only occur on hot summer days. Prolonged exposure even on snowy or overcast days can lead to burning. Preventive measures including sunscreen and sun-protective clothing can greatly reduce your risk.

Over time, excessive sun exposure can lead to skin damage, premature skin aging, and skin cancer. A history of severe sunburn gives you a 2.4-fold increase in your risk of squamous cell carcinoma and a 1.5-fold increase in the risk of melanoma.

Treating Sunburn

You can treat mild sunburn with a cool bath or shower, cool compresses, and an over-the-counter moisturizing cream.

For pain, you can take a nonsteroidal anti-inflammatory drug (NSAID) like Advil (ibuprofen) or Tylenol (acetaminophen).

If blisters form, do not break them.


Dehydration is the depletion or imbalance of fluids or electrolytes that interferes with the normal body functions. It occurs when the loss of body fluids exceeds the intake of fluids, usually on hot days when you are overexerting yourself.

Symptoms of Dehydration

Most healthy people can tolerate between a 3% to 4% loss of body water without symptoms.

After 5%, you may develop:

  • Dizziness
  • Headaches
  • Fatigue

As the water loss exceeds 10%, severe symptoms can develop, including:

  • Decreased urination
  • Confusion
  • Seizures

Treating Dehydration

Mild dehydration can usually be resolved by drinking water or an electrolyte-rich sports drink.

The best way to avoid dehydration is to drink water before you get thirsty, especially if you plan to be in the sun for a long period or are overexerting yourself.


The opposite of dehydration is a condition known as hyponatremia (sometimes referred to as "water intoxication").

Hyponatremia can occur when you lose a lot of water through sweat but fail to replace lost sodium when you rehydrate. People often think of dehydration as the loss of water when, in fact, it also includes an imbalance of electrolytes.

Hyponatremia Symptoms

Hyponatremia can occur during endurance sports when you lose too much fluid but only drink water. Unless you replace the lost sodium, you can begin to feel the effects of the depletion, including:

  • Headache
  • Fatigue
  • Lethargy
  • Loss of appetite
  • Irritability
  • Muscle weakness
  • Cramps
  • Confusion

Treating Hyponatremia

Mild hyponatremia can usually be resolved by drinking an electrolyte-rich sports drink.

Severe cases usually require a 3% saline solution delivered intravenously (into a vein) by emergency medical personnel.

Heat Exhaustion

Dehydration coupled with prolonged sun or heat exposure can cause heat exhaustion.

By definition, heat exhaustion occurs when the body's core temperature rises above 98.6° F (30° F) but not beyond 104° F (40° C). It typically occurs on hot, humid days when you're overexerting yourself.

Risk of Heat Exhaustion

Dehydration and obesity greatly increase the risk of heat exhaustion, as do:

  • Alcohol
  • Caffeine
  • Certain drugs (diuretics, antihistamines, beta-blockers, alcohol, ecstasy, and amphetamines)

Babies and the elderly are at greatest risk as they tend to have impaired thermoregulation (the ability of the body to adjust to climate changes).

Heat Exhaustion Symptoms

Common symptoms include:

  • Dizziness
  • Headache
  • Nausea
  • Thirst
  • Weakness
  • High body temperature
  • Profuse sweating
  • Decreased urination
  • Vomiting

Treating Heat Exhaustion

If someone you know has heat exhaustion:

  • Move them to a cool space
  • Remove any excess clothing
  • Bring down body temperature by fanning them or placing cool, wet towels on their skin
  • Offer water or a sports drink if they can keep fluids down
  • If dizziness occurs, lie them on their back and elevate their feet

If first aid measures fail to provide relief within 15 minutes, call 911 or seek emergency medical care. If left untreated, heat exhaustion can lead to heatstroke.


Heatstroke, also known as sunstroke, is a more severe form of heat exhaustion in which the body's core temperature exceeds 104° F (40° C).

It causes more than 600 deaths in the United States each year, either because of excessive exertion in hot temperatures (referred to as exertional heatstroke) or certain conditions that impair thermoregulation (non-exertional or "classic" heatstroke).

Causes of Heatstroke

Common causes of classic heatstroke include:

  • Younger age
  • Older age
  • Alcohol
  • Stimulants
  • Certain medications

Death from heatstroke frequently occurs when younger children or the elderly are left in parked cars in direct sunlight, where temperatures can climb to 124° F to 153° F (51° C to 67° C).

Heatstroke Symptoms

Symptoms of heatstroke are more profound than heat exhaustion but can differ based on whether you have exertional or classic heatstroke.

For instance, sweating is characteristic of exertional heatstroke but typically absent with classic heatstroke.

Other symptoms may include:

  • Rapid breath
  • Fast, weak pulse
  • Nausea and vomiting
  • Confusion or delirium
  • Hostility
  • Intoxication-like behavior
  • Fainting and unconsciousness
  • Seizures, especially in children

As symptoms advance, skin can suddenly take on a bluish tinge as blood vessels begin to narrow and restrict blood flow and oxygen exchange.

If left untreated, heatstroke can lead to:

  • Organ failure
  • Rhabdomyolysis (the breakdown of skeletal muscle)
  • Death

Treating Heatstroke

Heatstroke is an emergency. Treatment involves:

  • Rapidly cooling the body
  • Oral and IV rehydration
  • Standard resuscitation measures by trained medical professionals
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14 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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