Why does even 5 minutes of sun cause headache - and 10 mins cause nausea?

Did you read through the Heat Exhaustion/Stroke symptoms article? I know, you have to click through consecutive pages, which is a bit time-consuming!

Since we're all different, we'll each have a different threshold and set of symptoms. For example, a few weeks ago, I had a 10K race in high heat and humidity. I knew I was in trouble inside mile 6 and headed straight to the medical tent after crossing the finish line and collapsed just as the medic reached for my arm. I was promptly treated for heat stroke.

Last Saturday, I had a mere 5 mile run, and it was about 76F/50% humidity at 6:30 a.m. About 45 minutes later, the temperature was pushing 80F, there was no cloud cover to protect us on our route, and the humidity was rising. Being in full sun all that time, I started feeling nauseated; worse, I was getting a nagging headache and felt like my head was heating up. Fortunately, my buddy and I were only a couple of blocks away from our finish.

Sunday, I had 8.5 miles to do, but there was a lovely breeze and lots of cloud cover. It was about 75F and maybe 45% humidity. We also had the advantage of two water stops along the route and long stretches of shady woods, so we could either cool off or stay relatively cool. At the finish, my buddy and I cooled off in the kid's water playscape in the park where we had our run. What was really weird is that my buddy was sweating profusely and drank about 40 ozs of water, while I wasn't sweating all that much and only went through 12 ozs of water.

The difference was in the intensity of the sun and the humidity level. Your body's cooling mechanism isn't as efficient in high humidity.

Here's an important section of that article:

page 2 - http://www.emedicinehealth.com/heat_exhaustion_and_heat_stroke/page2_em.htm

page 3 - http://www.emedicinehealth.com/heat_exhaustion_and_heat_stroke/page3_em.htm

Hope this helps.

I'm happy to find this here but sad theres no response because I have the same 'thing' as your husband.

I can only handle about 20 minutes in direct sunlight before I get a migraine like headache and start throwing up. The vomiting doesn't stop until I've passed out from exhaustion, then once I wake up I'm fine but this generally takes 8-24 hours.

You're right that it's not dehydration because it happens so quickly and I drink a lot of water anyway. It seriously feels like my brain is cooking in my skull but my body temp doesn't rocket and I'm not covered in sweat. It's all head related.

I'll keep an eye on this message board, hopefully someone can add some insight.

Thanks for posting!!!

His symptoms happen so quickly that it can't be lack of hydration unless he is generally dehydrated - I will ask him about his liquid intake while at work all day.

He said he did read somewhere that some people are very sun sensitive and show these symptoms within minutes but he's honestly the only person I know who is reduced to headaches and throwing up within minutes. Talk about super sensitive!

Thanks for your reply and the links -

The body has a natural cooling mechanism. But, if too much body fluid is lost through sweating, the body overheats. But, this may just be heat exhaustion. It's important to stay hydrated, and this is something I'm particularly aware of because I'm in marathon training in the heat of summer - yikes!

There was a comment during today's broadcast of the Tour de France about how the cyclists must be constantly hydrated on their hard climb into today's mountain stage, not only because of the heat but because of the amount of body fluid they lose to their exertion. Hydration helps the body's natural cooling mechanism. While we're not exerting ourselves to quite the same level, the heat can still take a toll on us if our bodies are not properly hydrated.

When the brain is affected by elevated body heat, the condition becomes dangerous. This is a heat stroke symptom.

Understanding Heat Related Symptoms

Heat Exhaustion and Heat Stroke Symptoms

Extreme heat A Deadly Risk for Older Adults