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I love the sun, but get dizzy after a while. What’s going on?

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The question

I'm a fairly healthy woman in my 40s and I try to spend a chunk of my weekends outside to compensate for my office-indoor lifestyle during the week. But I find that if I sit out in the sun for more than an hour, I get dizzy and sluggish, and have to go inside to rest. Why is this happening?

The answer

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While being in the sunshine can feel great and has known benefits for our mood and vitamin D levels, being outside for long periods of time can take its toll on the body.

It sounds like you're having mild symptoms that can be resolved with a few simple precautions, but it's important to listen to your body. Given that you are an otherwise healthy person, the symptoms you are experiencing are likely secondary to dehydration and overexposure to the sun.

As it warms up outdoors, the body keeps from overheating through two mechanisms: by increasing blood flow to the skin and by sweating. The increased blood flow to the skin brings warmth from our core to the skin surface, which allows heat to dissipate. If this doesn't do the trick, the sweat glands are activated and we begin to perspire.

Sweating increases heat loss from the skin through the process of evaporation. Both of these cooling mechanisms can lead to dehydration, if done to excess. And common symptoms of dehydration include lightheadedness, dizziness and fatigue.

Some people are more prone to overheating than others. High-risk groups include the elderly, young children, overweight individuals and people with heart conditions or low blood pressure.

Certain medications – including those used to treat mental health conditions and low blood pressure – may also interfere with our body's cooling mechanisms, making you more sensitive to heat and more prone to dehydration. If you are taking one of these medications, take special precautions, such as hydrating well and limiting time spent in the hot sun.

To fully enjoy the outdoors, everyone should consider the following precautions:

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1. Hydrate well: We lose a large amount of fluid in the heat, so drink enough water to compensate for this loss. If you are enjoying an alcohol-based beverage or something with caffeine in it, make sure you hydrate well because these drinks can deplete your fluid stores.

2. Avoid direct sunlight: The shade is generally 10 degrees cooler than direct sunlight, so taking breaks from sun-exposed areas will still allow you to be outdoors, but you'll be less likely to overheat.

3. Choose your time wisely and take breaks from the sun: Avoid the heat during the hottest time of the day, generally between 10 a.m. and 2 p.m. If you are planning on exercising, choose either early morning or late evening to avoid overheating. And if you are planning on a full day outdoors, take regular short breaks inside to cool off.

4. Cover up: Wear sunglasses, sunscreen and a hat to protect your eyes and prevent sunburns, which increase your body's temperature.

5. Dress appropriately: Lighter-coloured and loose-fitting clothes are less likely to absorb heat than darker, tighter ones.

6. Eat smaller meals: Digesting large meals generates more energy and heat, so smaller meals are better options if you're spending time outdoors.

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Although it sounds like your symptoms are mild and reversible, again, listen to your body. If these symptoms persist despite rest, hydration and getting out of the heat, you may be showing signs of heat stroke. People with heat stroke may have high body temperatures and disorientation, and may become unconscious. Heat stroke is potentially fatal. But by taking these precautions, you can fully enjoy the summer sunshine.

Send family doctor Sheila Wijayasingheyour questions at She will answer select questions, which could appear in The Globe and Mail and/or on The Globe and Mail web site. Your name will not be published if your question is chosen.

The content provided in The Globe and Mail's Ask a Health Expert centre is for information purposes only and is neither intended to be relied upon nor to be a substitute for professional medical advice, diagnosis or treatment.

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