Jellyfish

The tentacles of a jellyfish contain venom that can cause a painful or sometimes life-threatening sting. Stings are usually accidental, caused by carelessly handling a jellyfish, or swimming or wading among them.

Jellyfish Stings

A jellyfish sting may cause intense pain, rash and welts, and may progress to vomiting and muscle spasms. Severe reactions can cause difficulty breathing, coma, and death. For most jellyfish stings, putting vinegar on the stung areas helps deactivate the "stingers," or nematocysts. Some types of jellyfish stings (like the box jellyfish) require immediate medical care. Flood the area with vinegar and keep still until help arrives.

Stingrays

A stingray's tail has serrated spines that can cause cuts and puncture wounds. The spines also contain venom. Stingrays aren't aggressive so injury usually occurs when a person accidentally steps on one.

Stingray Sting

Sting symptoms can include sharp pain, bleeding from the wound, vomiting, chills, and paralysis. Death may even occur. Most stingray injuries require immediate medical care. If help isn't readily available, immerse the injured area in hot water, remove the stingers, and scrub the wound with soap and fresh water. Apply pressure to stop the bleeding.

Skin Reactions to Henna Tattoos

The FDA has received complaints of skin irritations and allergic reactions from henna temporary tattoos, especially so-called "black henna." Black henna may contain the "coal tar" color p-phenylenediamine, which can cause allergic reactions such as blistering or even scarring in some people. Henna itself is made from a plant and produces a brown or reddish-brown tint. Other ingredients are added to produce other colors, or to make the stain darker and last longer.

Poisonous Ivy, Oak, and Sumac

Contact with sap from poison ivy, oak, and sumac causes a rash in most people. It begins with redness and swelling at the contact site then becomes intensely itchy. Blistering appears within hours or a few days. The rash lasts up to two to three weeks. Prescription or over-the-counter medication may soothe the itching of mild rashes. For a severe rash, oral cortisone may be given. If the skin becomes infected, antibiotics may be necessary.

Seen here (left to right) are poison ivy, oak, and sumac.

Mosquito Bites

Mosquitoes aren't just annoying; scratching a bite can cause a skin infection, too. Mosquitoes can also carry West Nile virus, dengue fever, and other diseases. To protect yourself from mosquitoes, apply insect repellent and cover up when you go outdoors, use door and window screens, and get rid of standing water in your yard, which is where mosquitoes lay their eggs.

Ticks

If you enjoy the outdoors, be careful of ticks -- they can attach to you as you brush past grass and plants. Ticks don't always carry diseases, and most bites aren't serious. But they can carry diseases including Lyme disease and Rocky Mountain spotted fever. A bite can also trigger an allergic reaction. Be sure to remove a tick properly. To prevent tick bites, keep arms, legs, and head covered in grassy areas and use tick repellant.

Bee Stings

Most reactions to bee stings are mild, causing minor swelling, pain, and itching. Severe allergic reactions occur in some people, with symptoms including hives, swelling of the mouth or throat, and difficulty breathing. If you have a severe anaphylactic reaction, lie down and remove the stinger. Give yourself an epinephrine injection, if you have access to one, and get immediate medical care. If you don't have an allergic reaction, remove the stinger, clean the sting site, apply ice, and take an oral antihistamine for itching. A delay in removing the stinger increases the amount of venom you receive.

Chiggers

Chiggers are tiny mites found in tall grass or weeds. They attach to the skin by inserting tiny mouth parts to penetrate and liquefy the skin cells on which they feed. Their bites are painless. But after a few days of being attached to the skin, chiggers fall off -- leaving very itchy red welts. Over-the-counter products can help relieve the itch, but see a doctor if your skin appears infected or the welts seem to be spreading.

Flip-Flop Hazards

They may be fun and fashionable, but flip-flops offer little protection against stubbed toes, glass cuts, puncture wounds, or having a heavy object smash your foot. Another danger: insect and snake bites. Emergency room physicians on both sides of the country report seeing adults and children with snake bites to the feet while wearing flip-flops or sandals. Consider wearing close-toed shoes that offer better protection this summer.

Poisonous Snake Bites

The U.S is home to many poisonous snakes, including these four. Bite symptoms may include severe burning pain at the bite site, swelling that spreads out from the bite, weakness, trouble breathing, and changes in heart rate. Bite severity depends on many factors, including the amount of venom injected, bite location, and a person's age and health. Seek immediate medical care if you think you've been bitten by a poisonous snake.

Pictured here (clockwise from top left): coral snake, rattlesnake, water moccasin, copperhead.

Nonpoisonous Snake Bites

Most snakes that live in the U.S. are nonpoisonous and their bites don't cause serious health problems. A bite may leave fang marks or other puncture wounds that can be treated at home to relieve symptoms and prevent infection. However, large nonpoisonous snake bites, such as those from pythons or boa constrictors, can cause injury to skin, joints, bones, and muscles because of the force of the bite. See a doctor for these bites.

Seen here is an adult shorthead garter snake.

Black Widow Spiders

Wood piles and tree stumps -- that's where poisonous female black widows hide. The female has a bright-colored "hourglass" on the underside. Her bite may cause sharp, shooting pain up the limb, but it may also be painless. Look for one or two red fang marks, redness, tenderness, and a nodule at the bite site. Muscle cramps, nausea, vomiting, seizure, and rise in blood pressure may follow soon after a bite. Seek medical care if bitten.

Brown Recluse Spiders

Hiding in attics and closets -- in Midwestern and South central states -- that's where you'll find these spiders. They range in color from yellowish-tan to dark brown, with darker legs. Brown recluses have a "violin" pattern in the upper body, where legs attach. Their venom is extremely poisonous, and their bite can cause serious wounds and infection. The bite itself is often painless -- then skin reddens, turns white, develops a red "bull's-eye," blisters, and becomes painful. Bites warrant immediate medical care.

Burns from Fireworks

An estimated 8,800 people were treated in emergency rooms in 2009 for injuries related to fireworks. Most injuries involved the hands, eyes, head, face, and ears. Burns were the most common injury. Minor burns smaller than a person's palm can often be treated at home. Run it under cool water, then cover with a clean, dry cloth. Larger burns, and ones to the hands, feet, face, genitals, and major joints usually require emergency care.

Skin Cancer

Skin cancer is the most prevalent of all cancers in the U.S. An uncontrolled growth of abnormal skin cells, it results in tumors that are benign or malignant. There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, and melanoma. Consult a doctor if a mole or spot changes in size, shape, or color, has irregular edges, is more than one color, is asymmetrical, or itches, oozes, or bleeds.

Heat Rash

The result of blocked sweat ducts, heat rash looks like small pinkish pimples and is usually found on body areas covered by clothing. Most common in children, it may also affect adults in hot, humid climates. Most rashes heal on their own. To alleviate symptoms, apply cold compresses or take a cool bath. Air dry and avoid lotions. If baby's skin is irritable to the touch, ask your doctor about using calamine or hydrocortisone cream.

Sunburn

Too much exposure to the sun's UV rays can result in the redness and pain of sunburn. Sunburn usually appears within hours after sun exposure and may take weeks to fade. Pain relievers, cold compresses, aloe, hydrocortisone, or moisturizing creams may ease discomfort. Second-degree sunburn -- characterized by redness, swelling, and blistering – is usually more painful and takes longer to heal. See a doctor if you have a blistered sunburn. To prevent sunburn, use a sunscreen of SPF 30 or higher when outdoors.

More Reading on Summer Skin Hazards

• Jellyfish Sting FAQs
• How to Choose and Use Insect Repellents
• Poison Ivy, Oak & Sumac
• Stinging Insect Allergies
• Snake Bites
• Spider Bites: Black Widow and Brown Recluse
• Skin Cancer