Mosquitoes—Mosquito-borne diseases are rare in Hawaii, though an outbreak of dengue fever did affect Hawaii Island in 2016. The Hawaii State Health Department recommends travelers a) choose lodging with screens or sleep under a mosquito net; b) cover up in long sleeves and pants; and c) use EPA-registered insect repellent. For more info, visit the Centers for Disease Control and Prevention website at

Centipedes, Scorpions & Other Critters—Although insects can get a little close for comfort in Hawaii (expect to see ants, cockroaches, and other critters indoors, even in posh hotels), few cause serious trouble. Giant centipedes—as long as 8 inches—are occasionally seen; scorpions are rare. Around Hilo on the Big Island, little red fire ants can rain down from trees and sting unsuspecting passersby. If you're stung or bitten by an insect and experience extreme pain, swelling, nausea, or any other severe reaction, seek medical help immediately. Geckos—the little lizards circling your porch light—are harmless and considered good luck in Hawaiian homes. Yes, even inside homes.

Hiking Safety—Before you set out on a hike, let someone know where you’re heading and when you plan to return; too many hikers spend cold nights in the wilderness because they don’t take this simple precaution. It’s always a good idea to hike with a pal. Select your route based on your own fitness level. Check weather conditions with the National Weather Service ( on Oahu), even if it looks sunny: The weather here ranges from blistering hot to freezing cold and can change in a matter of hours or miles. Do not hike if rain or a storm is predicted; flash floods are common in Hawaii and have resulted in many preventable deaths. Plan to finish your hike at least an hour before sunset; because Hawaii is so close to the equator, it does not have a twilight period, and thus it gets dark quickly after the sun sets. Wear sturdy shoes, a hat, clothes to protect you from the sun and from getting scratches, and high-SPF sunscreen on all exposed areas. Take plenty of water, basic first aid, a snack, and a bag to pack out what you pack in. Watch your step. Loose lava rocks are famous for twisting ankles. Don’t rely on cellphones; service isn’t available in many remote places.

Vog—When molten lava from Kilauea pours into the ocean, gases are released, resulting in a brownish, volcanic haze that hovers at the horizon. Some people claim that exposure to the smog-like air causes headaches and bronchial ailments. To date, there’s no evidence that vog causes lingering damage to healthy individuals. Vog primarily affects the Big Island—Kona, in particular—but is often felt as far away as Maui and Oahu. You can minimize the effects of vog by closing your windows and using an air conditioner indoors. The University of Hawaii recommends draping a floor fan with a wet cloth saturated in a thin paste of baking soda and water, which captures and neutralizes the sulfur compounds. Cleansing your sinuses with a neti pot and saltwater also helps. Word of caution: If you’re pregnant or have heart or breathing problems, avoid exposure to the sulfuric fumes in and around Hawaii Volcanoes National Park.

Ocean Safety—The range of watersports available here is astounding—this is a prime water playground with conditions for every age and ability. But the ocean is also an untamed wilderness; don’t expect a calm swimming pool. Many people who visit Hawaii underestimate the power of the ocean. With just a few precautions, your Pacific experience can be a safe and happy one. Before jumping in, familiarize yourself with your equipment. If you’re snorkeling, make sure you feel at ease breathing and clearing water from the snorkel. Take a moment to watch where others are swimming. Observe weather conditions, swells, and possible riptides. If you get caught in big surf, dive underneath each wave until the swell subsides. Never turn your back to the ocean; rogue waves catch even experienced water folk unaware. Be realistic about your fitness—more than one visitor has ended his or her vacation with a heart attack in the water. Don’t go out alone, or during a storm.

Note that sharks are not a big problem in Hawaii; in fact, local divers look forward to seeing them. Only 2 of the 40 shark species present in Hawaiian waters are known to bite humans, and then usually it’s by accident. But here are the general rules for avoiding sharks: Don’t swim at dusk or in murky water—sharks may mistake you for one of their usual meals. It should be obvious not to swim where there are bloody fish in the water, as sharks become aggressive around blood.

Seasickness—The waters in Hawaii range from calm as glass (off the Kona Coast on the Big Island) to downright turbulent (in storm conditions) and usually fall somewhere in between. In general, expect rougher conditions in winter than in summer and on windward coastlines versus calm, leeward coastlines. If you’ve never been out on a boat, or if you’ve been seasick in the past, you might want to heed the following suggestions:

* The day before you go out on the boat, avoid alcohol, caffeine, citrus and other acidic juices, and greasy, spicy, or hard-to-digest foods.

* Get a good night’s sleep the night before.

* Take or use whatever seasickness prevention works best for you—medication, an acupressure wristband, ginger tea or capsules, or any combination. But do it before you board; once you set sail, it’s generally too late.

* While you’re on the boat, stay as low and as near the center of the boat as possible. Avoid the fumes (especially if it’s a diesel boat); stay out in the fresh air and watch the horizon. Do not read.

* If you start to feel queasy, drink clear fluids like water, and eat something bland, such as a soda cracker.

Stings—The most common stings in Hawaii come from jellyfish, particularly Portuguese man-of-war and box jellyfish. Since the poisons they inject are very different, you’ll need to treat each type of sting differently.

A bluish-purple floating bubble with a long tail, the Portuguese man-of-war is responsible for some 6,500 stings a year on Oahu alone. Although painful and a nuisance, these stings are rarely harmful; fewer than 1 in 1,000 requires medical treatment. The best prevention is to watch for these floating bubbles as you snorkel (look for the hanging tentacles below the surface). Get out of the water if anyone near you spots these jellyfish. Reactions to stings range from mild burning and reddening to severe welts and blisters. Most jellyfish stings disappear by themselves within 15 to 20 minutes if you do nothing at all to treat them. All Stings Considered: First Aid and Medical Treatment of Hawaii’s Marine Injuries, by Craig Thomas, M.D., and Susan Scott (University of Hawaii Press, 1997), recommends the following treatment: First, pick off any visible tentacles with a gloved hand or a stick; then, rinse the sting with salt- or fresh water, and apply ice to prevent swelling. Avoid applying vinegar, baking soda, or urine to the wound, which may actually cause further damage. See a doctor if pain persists or a rash or other symptoms develop.

Transparent, square-shaped box jellyfish are nearly impossible to see in the water. Fortunately, they seem to follow a monthly cycle: 8 to 10 days after the full moon, they appear in the waters on the leeward side of each island and hang around for about 3 days. Also, they seem to sting more in the morning, when they’re on or near the surface. The stings from a box jellyfish can cause hive-like welts, blisters, and pain lasting from 10 minutes to 8 hours. All Stings Considered recommends the following treatment: First, pour regular household vinegar on the sting; this will stop additional burning. Do not rub the area. Pick off any vinegar-soaked tentacles with a stick and apply an ice pack. Seek medical treatment if you experience shortness of breath, weakness, palpitations, or any other severe symptoms.

Punctures—Most sea-related punctures come from stepping on or brushing against the needle-like spines of sea urchins (known locally as wana). Be careful when you’re in the water; don’t put your foot down (even if you are wearing booties or fins) if you can’t clearly see the bottom. Waves can push you into wana in a surge zone in shallow water. The spines can even puncture a wet suit. A sea urchin puncture can result in burning, aching, swelling, and discoloration (black or purple) around the area where the spines entered your skin. The best thing to do is to pull out any protruding spines. The body will absorb the spines within 24 hours to 3 weeks, or the remainder of the spines will work themselves out. Again, contrary to popular thought, urinating or pouring vinegar on the embedded spines will not help.

Cuts—Stay out of the ocean if you have an open cut, wound, or new tattoo. The high level of bacteria present in the water means that even small wounds can become infected. Staphylococcus, or “staph,” infections start out as swollen, pinkish skin tissue around the wound that spreads and grows rather than dries and heals. Scrub any cuts well with fresh water and avoid the ocean until they heal. Consult a doctor if your wound shows signs of infection.

Also see “Fast Facts” in the individual island chapters for listings of local doctors, dentists, hospitals, and emergency numbers.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.