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It's a sweltering summer day, so you take a big sip of a refreshing, frozen coffee--and you're immediately doubled over with throbbing head pain.

Why do frosty foods give us headaches? New research has shed light on the possible causes (and cures) of the phenomenon known as brain freeze.

When a frozen treat comes in contact with the roof of your mouth, it triggers nerves that alert your brain of the temperature change. In response, the anterior cerebral artery dilates and increases blood flow to the brain's frontal lobe to help keep it warm and protected, says Jorge Serrador, M.D. of Harvard Medical School, lead researcher on a recent study which identified the mechanisms at work during what's commonly called brain freeze.

Researchers believe that the additional blood flow to the frontal lobe increases pressure in the skull, which brain receptors process as pain. This could explain why the frontal lobe is the area of the brain that feels "frozen" post-popsicle, Serrador says.

Here are three ways to avoid the big chill:

1. Tongue It
Can you curl your tongue? Good. Fold the tip of it backward and stick the bottom of your tongue to the roof of your mouth. The warmth will help heat up the nerves in your palette and cause the blood flow to your brain to normalize, Serrador says.

2. Slurp Slowly
To make study participants get brain freeze, Serrador had them suck down ice water like thirsty maniacs. Why? "The only way to get a brain freeze is to drink or eat whatever it is [that's cold] really fast," he says. If you drink (or eat) more slowly, you give your blood time to heat the tissue in the roof of your mouth and avoid triggering a cold-induced headache. So slow down and savor your treat.

3. Warm Your Hands
Your hands might not be cold, but acting like they are can make your mouth warmer, Serrador says. Cup your hands around your mouth like you would in the winter and exhale deeply. It will trap warm air in your mouth and help thaw your noggin.

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People, stop peeing on people.

This could prevent some awkward beach encounters this summer: Turns out, urine does not ease the pain from jellyfish stings -- regardless of what your "Friends" told you.

Actually, you're better off using vinegar -- or, if that's not in your beach bag, ocean water -- as urine just doesn't have the right chemical makeup to neutralize the sting, reports The Telegraph today quoting head of British Red Cross first aid Joe Mulligan.

“If people have been stung, they need to get out of the water to avoid getting stung again. Once out, slowly pouring seawater over the sting will help ease the pain.

“Doing the same thing with vinegar can be even more effective as the acid helps neutralise the jellyfish sting. But, unless you’re near a chip shop, seawater will probably be easier to find.”

Emergency physician Dr. Ryan Stanton, who's spent some time in Australia and is familiar with the country's venomous box jellyfish, agrees. The efficacy hierarchy here is this: vinegar, isopropyl alcohol, ocean water -- then urine, explains Stanton, now the medical director at UK HealthCare Good Samaritan Hospital in Lexington, Ky.

The acidic chemicals in the vinegar, alcohol and even the seawater neutralize the sting and deactivate the nemotocysts -- the stinging cells that inject the creature's venom into your skin. The problem with urine, Stanton explains, is that it's just too variable: If it's concentrated, it may work OK, but from a well-hydrated person, it won't be much different than plain old water.

Next, rid your skin of the nematocysts. Wash them off with saltwater, or use something with a well-defined edge (like a credit card) to remove the cells from your skin.

In Australia, Stanton says, every lifeguard stand has a bottle of vinegar, as do many in Hawaii. But that's likely not the case at most American beaches.

"Basically, I recommend if you're going to a beach, it's not a bad idea to take a little bottle of vinegar; it's super cheap and it can be very helpful," says Stanton, who's also a spokesperson for the American College of Emergency Physicians. "But I would not recommend that you go to a beach and start urinating on each other."

Follow Melissa Dahl on Twitter: @melissadahl

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Scorching temperatures can challenge even the sunniest of dispositions -- but it makes some genuinely SAD.

Many of us can hardly wait for summer to arrive, but a small number of people are much happier when it's over. You've no doubt heard of Seasonal Affective Disorder, the wintertime mood disorder -- but some get SAD in the summer.

As hot weather approaches, those with summer SAD sleep less, eat less, and lose weight. They're extremely irritable and agitated. (It's the reverse for people with winter SAD, who sleep more, gain weight and crave high-carb foods, and tend to slow down and socially hibernate from late fall to early spring.)

Summer-onset depression is thought to affect less than 1 percent of the population, making it much rarer than the winter variety experienced by an estimated 5 percent of people.

In its most severe form, people with summer seasonal depression may be more at risk for suicide than cold-weather SAD, says Dr. Norman Rosenthal, a clinical professor of psychiatry at Georgetown University Medical School, who has studied both types and first helped discover their existence. "Suicide is more of a concern when people are depressed and agitated rather than depressed and lethargic," he explains.

When summer depression was first recognized in 1986, Rosenthal said that mental health professionals suspected the cause was the heat and humidity. That, he said, lent itself to the idea that a cold shower, air conditioning, swimming in cold lakes or heading North would relieve symptoms. Although these treatments for hot-weather depression are useful for some, they lack the staying power that light-box therapy has on winter SAD. 

'The light is cutting though me like a knife'
A person with summer SAD can stay inside, crank up the AC, and darken the room but then go outside into the heat and it's as if they've never been treated, explains Rosenthal, the author of "Winter Blues."

Another idea is that it might be the light itself that's aggravating sufferers, whether it's the intensity of sunlight or the angle it's coming at people. One of Rosenthal's summer depression patients describes it as "feeling like the light is cutting though me like a knife."

Still another possibility is that there may be two kinds of warm-weather depression, says Dr. Alfred Lewy, a professor of psychiatry at Oregon Health & Science University in Portland. He suggests there might be one group of people who have an unpleasant reaction to the heat and humidity -- a discomfort with the climate. But even in Portland where summers aren't that hot or humid, he's seen patients struggle with summer depression.

Lewy suspects the cause in a second group might be that the body's natural clock, it's circadian rhythms, are misaligning in summer. Instead of cueing to dawn, the longer daylight is causing some vulnerable people to cue to dusk. Cueing to dusk shortens the typical body clock and delays a person's sleep-wake cycle. This mismatch, theorizes Lewy, may be triggering depression.

He successfully treated a person with summer depression with a combination of getting early morning sunlight (30 to 60 minutes daily), which shifts the body clock forward, and low-dose melatonin, a hormone that helps regulate sleep-wake cycles. Severe symptoms may also benefit from antidepressants.

Do you secretly -- or perhaps not-so-secretly -- loathe the summer months? What helps you get through them?

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Ahhh.

Ever notice that you sleep like a baby on a hammock? Maybe it's just the slow, soothing rocking motion that reminds grown-ups of being in a parent's arms until their little eyelids finally close.

Inspired by that concept, some Swiss scientists decided to examine the idea of rocking a person to sleep. Researchers wondered whether the see-sawing movement would make adults drift off sooner and how it affected sleep quality.

So they developed an "experimental hammock" -- a custom-made bed that gently swayed from side to side. They asked 12 participants, all of them men ages 22 to 38, who were all good sleepers, to take a 45-minute afternoon nap in this cradle for grown-ups.

They monitored the volunteers' brain waves throughout the nap and compared the results to having these same participants nap in the same bed without any rocking motion. The research appears in the June 21 issue of Current Biology.

"We observed a faster transition to sleep in each and every participant in the swinging condition," says Sophie Schwartz, a neuroscientist at the Sleep and Cognition Neuroimaging Lab at the University of Geneva in Switzerland and the study's lead author.

"Not only does rocking make us fall asleep more quickly, but it also makes people sleep more deeply throughout the nap," she explains.

Compared to nodding off in a stationary bed, those napping in a swinging one had a longer duration of N2 sleep, a type of non-rapid eye movement sleep that makes up about half a night's shuteye. Scientists also observed a dramatic boost in brain-wave patterns seen in deep sleep. 

"Motion has specific effects on the brain, and this is precisely what our study shows," says Schwartz. Although researchers expected that rocking would make volunteers conk out sooner, they were surprised it changed the quality of sleep and in such a sustained manner.

Now that they've seen how rocking affects a short nap in healthy adults, the next step is to see how it benefits an entire night's sleep. Other questions they might research include whether the brain changes seen in adults from rocking are also observed in babies, whether motion improves sleep in those with insomnia, and whether it has positive effects on waking performance.

Still there's no need to wait for answers. This summer, put science to the test: Find yourself a hammock or rocking chair in the shade and enjoy that time-honored tradition in some cultures -- the siesta.

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Imagine what your life would be like if your hands were always dripping in sweat: You'd make up excuses after giving a clammy handshake. You'd worry about your touch devices slipping out of your hands.

You'd avoid reading print editions of the newspaper to prevent staining your skin and clothes with ink. And you may even shy away from holding hands with your sweetheart.

Sophia Wastler, 36, of Virginia Beach, Va., has lived through all these situations. "You just think you're a weird freak and you suffer in silence," she admits.

Wastler also recalls being asked to go barefoot in modern dance class, and feeling embarrassed after leaving huge puddles at her feet and mortified when wiping them up.

It took Wastler until she was 31 to learn why her underarms, palms and soles of her feet were constantly soaked. She had gone to see a new doctor (not because of the sweating), and instead of giving her usual excuse after shaking his hand and leaving it moist, she blurted out, "My hands are always sweaty."

Then the doctor told her, "You have hyperhidrosis." That's the first time Wastler heard of a medical condition that causes excessive sweating.

"Primary focal hyperhidrosis is when you're sweating excessively for the physiological requirements at that time, and it's not related to any other medical problem or a side effect of a medication," explains Dr. Dee Anna Glaser, a professor of dermatology at Saint Louis University School of Medicine.

For example, if you're sitting indoors, watching TV, and you're drenched in sweat -- far more than others around you -- that's not healthy sweating, which is simply keeping your body cool. It's extreme and excessive perspiration.

Extreme sweating, when it's from diabetes, night sweats or menopausal hot flashes, typically occurs all over the body. But in primary hyperhidrosis, a person sweats profusely in certain areas, most commonly the armpits, palms or face. It may also occur on the scalp, soles of the feet, in the groin area or along the breast tissue.

Hyperhidrosis often begins in childhood or adolescence, and it tends to run in families. "But there's such a negative stigma about sweating that people often don't talk about it or think it's them -- they need to shower more or find the right deodorant," explains Glaser.

"Most people don't realize that excessive sweating is a condition and there's treatment for it," she says.

Hyperhidrosis sufferers have normal sweat glands, in terms of their size, number and function. So researchers suspect the cause has something to do with the signal coming from the brain, which is telling the sweat glands to produce wetness when it's not necessary, points out Glaser.

Treatment often starts with clinical strength antiperspirants available over the counter or by prescription. Botox injections every six or seven months into the affected are also effective.

That's what did the trick for Wastler and is currently keeping her hands dry. She also uses moisture-absorbing insoles for her feet.

"Life began for me at 31," Wastler admits, which is why she also recommends finding a doctorwho knows and understands hyperhidrosis. 

Here are some interesting facts about the condition: 

• People with hyperhidrosis may sweat 4 to 5 times more than normal.
• Athletes perspire more than other people because their bodies have become super efficient at keeping cool.
• Men sweat more than women, although both men and women suffer equally from hyperhidrosis. (But more women seek out treatment for it.)
• It's OK to use antiperspirant on your hands and feet if you tend to sweat a lot there.
• Consider applying antiperspirant before bedtime so the active ingredients soak into your pores and block morning sweating.

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Some folks seem to be magnets for mosquitoes, while others rarely get bitten. What makes the little buggers single you out and not the guy or gal you're standing next to at the Memorial Day backyard barbecue?

The two most important reasons a mosquito is attracted to you have to do with sight and smell, says Jonathan Day, a professor of medical entomology at the University of Florida in Vero Beach. Lab studies suggest that 20 percent of people are high attractor types, he says.

Mosquitoes are highly visual, especially later in the afternoon, and their first mode of search for humans is through vision, explains Day. People dressed in dark colors -- black, navy blue, red -- stand out and movement is another cue.

Once the mosquito keys in on a promising visual target, she (and it's always "she" -- only the ladies bite) then picks up on smell. The main attractor is your rate of carbon dioxide production with every exhale you take. 

Those with higher metabolic rates produce more carbon dioxide, as do larger people and pregnant women. Although carbon dioxide is the primary attractant, other secondary smells coming from your skin or breath mark you as a good landing spot.

Lactic acid (given off while exercising), acetone (a chemical released in your breath), and estradiol (a breakdown product of estrogen) can all be released at varying concentrations and lure in mosquitoes, says Day. Your body temperature, or warmth, can also make a difference. Mosquitoes may flock to pregnant women because of their extra body heat.

But with more than 350 compounds isolated from odors produced by human skin, researchers have barely scratched the surface behind a mosquito's preference for certain people, says Joseph Conlon, a medical entomologist and the technical advisor to the American Mosquito Control Association.

Although it may all boil down to human odor and genetics -- studies of twins have revealed they tend to be attractive or repellant to mosquitoes in the same measure -- it's more complicated than that, suggests Conlon.

He says the latest thinking is that it might not be about what makes people more attractive to mosquitoes, but what makes them not as repellant. It could be that individuals who get less bites produce chemicals on their skin that make them more repellant and cover up smells that mosquitoes find attractive.

Mosquitoes don't bite you for food, since they feed off plant nectar, Conlon explains. Females suck your blood to get a protein needed to develop their eggs, which can then send more pesky insects into the world to annoy you.

But keep this in mind when you're outdoors this summer: Mosquitoes are more attracted to people after they drink a 12-ounce beer. It could be that people breathe a little harder after a cold one or their skin is a little warmer, suggests Conlon. But that won't stop him from having a brewski, even though he considers himself a mosquito magnet.

Here are more fun facts about mosquitoes and bites provided by our experts:

• Eating bananas will not attract mosquitoes and taking vitamin B-12 will not repel them; these are old wives' tales.
• Some mosquito species are leg and ankle biters; they cue into the stinky smell of bacteria on your feet.
• Other species prefer the head, neck and arms perhaps because of the warmth, smells emitted by your skin, and closeness to carbon dioxide released by your mouth. 
• The size of a mosquito bite welt has nothing to do with the amount of blood taken and everything to do with how your immune system responds to the saliva introduced by the mosquito into your skin.
• The more times you get bitten by a particular species of mosquito, the less most people react to that species over time. The bad news? There's more than 3,000 species worldwide.

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