Press Release

Taking the Sting Out of Summer: Advice from Stanford Wilderness Medicine Experts


Stanford wilderness medicine experts offer advice on dealing with summer hazards. 

Consider the yellowjacket. The ornery, covetous yellowjacket. That turkey sandwich you were eating at a table outside your workplace? That's hers now. If you have the gall to try to reclaim your lunch, you could pay a painful price.

But wasps are just one of several stinging or biting critters that can trip up a beautiful summer day in the Bay Area; there are also mosquitoes, rattlesnakes, ticks and jellyfish. 

As it happens, Stanford Hospital & Clinics has perhaps the foremost concentration of wilderness medicine physicians in the nation, including emergency medicine physician Paul Auerbach, MD, who with a team of experts wrote the definitive book on the subject, the roughly 2,300-page Wilderness Medicine (now in its sixth edition). It covers virtually everything that could give you trouble outdoors: bear attacks, sprains, altitude sickness, drowning, lightning, sunburn, heatstroke, volcanic eruptions, blisters — you name it. (Click here to see an article on blisters and blister care.)

Those looking for something lighter can turn to Auerbach's paperback, Medicine for the Outdoors, which, at a little more than 500 pages, covers much of the important ground. Both books were consulted in writing this article, as was Auerbach himself and fellow Stanford wilderness medicine experts Robert Norris, MD, chief of emergency medicine, and Grant Lipman, MD, an emergency medicine physician and adventure race medical expert. 

Mosquitoes and jellyfish

With the warm weather comes one of the season's more ubiquitous pests: the mosquito. To foil these bloodsucking arthropods, there are essentially two preventive measures you can take: a physical barrier or insect repellent, or both, Auerbach said. "Wear something that covers your arms and legs," he said. "Light-colored clothing is less attractive to mosquitoes. Insect repellent, especially one with DEET [N,N-Diethyl-meta-toluamide], is quite effective."

Worse than its itchy bite, however, is the insect's potential as a vector for infectious disease, such as West Nile virus. About 20 percent of people infected with the virus will develop flu-like symptoms in three to 14 days. Fewer than 1 percent of those infected suffer more serious health problems, such as encephalitis or meningitis. (In 2011, there were 158 reported cases of West Nile virus among people in California and nine reported fatalities, according to the state Department of Public Health.)

Unlike mosquitoes, jellyfish are not interested in preying on you. People are stung by these brainless, gelatinous sea animals when they accidentally brush up against them or try to handle them. Luckily, species off the California coast are likely to inflict only mild or moderate pain, if any, Auerbach said. The Portuguese man-of-war is rarely sighted in Northern California waters.

If you know you're going to be sharing the water with jellyfish, wear a wetsuit or synthetic-nylon dive skin, and give jellies wide berth, he said. Do not touch jellyfish in the water or on the beach.

If you are stung by a jellyfish, rinse the wound with seawater; do not use fresh water, as this may increase envenomation by stimulating more nematocysts, the jelly's stinging cells, which become embedded in the skin, Auerbach said. Remove any attached tentacles with forceps or a gloved hand. Apply a soak-compress of vinegar or isopropyl rubbing alcohol to the wound for about 30 minutes or until the pain subsides. Then apply a lather of shaving cream and shave the affected area with a safety razor to remove any remaining nematocysts. If the stinging sensation persists, reapply the vinegar or rubbing alcohol for another 15 minutes. Auerbach also advised being prepared for a possible allergic reaction. Symptoms may include difficulty breathing, difficulty swallowing, hives, a swollen tongue or collapse. In such cases, call 9-1-1 and use an epinephrine auto-injector, such as an EpiPen, if one is available.

A blue- to purple-colored jellyfish-like creature, the by-the-wind sailor (Velella velella), often washes up on West Coast beaches in large numbers during the spring and early summer, Auerbach noted. People sometimes confuse these small, plankton-eating hydrozoa — usually measuring only a few inches in width — with the much larger Portuguese man-of-war. Although Velella are considered mostly harmless to humans, Auerbach advised against touching them, which could cause skin irritation. 

Rattlesnakes and ticks

"They would much rather be left alone, given the chance," Norris said. "They," in this instance, are northern Pacific rattlesnakes, Northern California's only native species of venomous snake.

An internationally recognized expert on venomous snake bites, Norris said that the Bay Area has a healthy population of these pit vipers. They are generally active April through September but will sometimes emerge from hibernating in places like rodent holes, crevices and rock piles on warm winter or late-autumn days to sun themselves. "They are not deep hibernators," Norris said.

You can find them in grasslands, the woods, on hiking trails— "really, just about anywhere," Norris said. "I've seen some patients who were bitten in Palo Alto; one was in her garden when it happened."

If a rattlesnake crosses your path, give it the right of way. If it's not moving, you can walk around it, making sure to stay at least several feet away, he said. The good news is that these snakes are not aggressive: If they feel threatened, they will generally try to slither away or give their infamous warning rattle (one caveat: some may have lost or not yet grown rattles). Their venom is fairly toxic, but very few people actually die from bites. Annually, there are some 8,000 venomous snake bites nationwide, resulting in only about six deaths, Norris said.

To prevent bites, look where you're putting your feet and hands. Wear hiking shoes and long pants, Norris said. "Be alert, and don't step over logs," he added. "If you're going through tall grass, use a walking stick to probe in front of you. The snake will often let you know it's there."

If you're bitten, get medical care as soon as you can. If possible, call 9-1-1 and immobilize the affected extremity using a splint, but don't compress the wound, Norris said. "Don't worry about other first aid," he said. "If you're in the wilderness, do whatever you need to get to a hospital, even if it means walking for a couple of hours. Time is the issue." As long as bite victims are given antivenom within a few hours, their lives are rarely in danger, he said. 

Unlike the rattlesnake, the tick, another denizen of the California wilderness, has an incentive to bite you: Your blood could make for a satisfying meal. There are roughly a half-dozen tick species in California that will attach themselves to humans, but it's the western blacklegged tick that is the most notorious; it is a known vector for Lyme disease, the most common tick-borne disease in the state.

Immature ticks, known as nymphs, are about the size of a poppy seed, and they're the most likely to be carrying the disease-causing bacteria. They like to hang out among leaves and fir needles on woodland floors. They also will climb up on logs and the lower trunks and branches of trees. Adult ticks, which are less likely to carry the bacteria, like to sit on grasses and on bushes, waiting to latch on to prey. 

When hiking in woodlands, grasslands or chaparral or along hillside trails, wear light-colored clothes that cover your arms and legs, and tuck pants into socks, Norris advised. Check your clothes and exposed parts of your body, including your scalp, for ticks every few hours. Also, insect repellents with DEET are effective deterrents, he said. 

If a tick manages to dig its mouthparts into your skin, remove it with tweezers: grasp the bug as close to the skin as possible and pull steadily. Don't jerk or twist; this may leave mouthparts in the skin, Norris said. Wash your hands and clean the wound with soap and water before applying a mild antiseptic. It also may be useful to save the tick, in case it's needed later for identification or lab tests.

Lyme disease is not likely to be transmitted if the tick was attached to you for less than 48 hours, Norris said. In about 75 percent of infected people, a slowly spreading, bull's-eye-shaped skin rash appears three to 32 days after the bite. The average onset time of the rash is seven to 10 days. Other early signs of the disease include flu-like symptoms.

Other tick-borne diseases, such as Rocky Mountain spotted fever and relapsing fever, are rare in California. However, if you observe a rash or feel flu-like symptoms — fever, muscle aches, chills — in the days or weeks following a tick bite or suspected bite, seek medical help. Most tick-borne diseases, including Lyme disease, can be successfully treated with antibiotics, especially if treatment begins early.


Yellowjackets are social wasps, sometimes confused with honeybees, and they typically become a problem for picnickers and other al fresco diners beginning in August.

"Cover your food and keep a tight lid on trash cans," Lipman advised. Don't swat at the wasps; this can make them mad, and, unlike bees, they are able to sting repeatedly, he added. Avoid crushing them, which releases a pheromone that acts as kind of chemical alarm and may encourage other nearby wasps to attack. Steer clear of their nests, commonly found in rodent burrows, wall cavities, attics, old tree stumps and under eaves.

To treat the sting, quickly remove the stinger if it is embedded in the skin — though this usually doesn't happen in the case of wasp stings — brushing it off with the edge of a fingernail or a credit card, or pulling it out with your fingers or tweezers, Lipman said. (However, if tweezers are used, take care not to crush the stinger, which can release more venom.) Then apply ice or a cold compress to the sting — 20 minutes on, 20 minutes off. Over-the-counter pain medications, such as acetaminophen or ibuprofen, may offer some relief, as may a local antihistamine lotion applied to the sting area. Expect swelling, redness and possible blistering. Some people may experience nausea, vomiting or intestinal cramping. If you suspect an allergic reaction to a sting, call 9-1-1. If you have a history of allergic reactions to insect stings, it's advisable to keep an epinephrine auto-injector, such as the EpiPen, on hand, Lipman said.

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