Jellyfish stings are among the most common incidents that happen to beachgoers, snorkelers and swimmers. Therefore, these creatures are feared by most people, even though most species are harmless or cause only short-term discomfort if contacted. To break down the misconceptions and clarify real potential threats, here we discuss the most important information about jellies along with a step-by-step guide on what to do when stung by a jellyfish and some tips on how to avoid encountering them.
Table of Contents
- What are jellyfish?
- Where are jellies found?
- How do jellyfish sting?
- Do all jellyfish sting?
- Jellyfish sting symptoms
- What does a jellyfish sting look like?
- How to treat a jellyfish sting?
- How long does a jellyfish sting last?
- Severe reactions
- Delayed reaction to jellyfish sting
- Can jellyfish sting when dead?
- Most dangerous jellyfish in the world
- How to prevent jellyfish stings?
- Why are there so many jellyfish?
What are jellyfish?
Jellyfish -often called jellies, sea jellies and medusas- are some of the most fascinating and bizarre creatures on the earth. They are not fish but belong to the group of invertebrates, are related to sea anemones and corals and are composed of a jellylike substance that consists of about 95% water and only 5% of structural proteins like nerves and muscles. Their dome, mushroom or bell-shaped body is ringed with numerous tentacles.
Jellies have no heart, bones or eyes. They do not have brains either; they detect their surroundings through the nerves at the base of their tentacles.
Most jellies have limited control over their movements. By expanding and contracting their bell, they propel themselves forward and usually drift in currents. Therefore, they are often found in large masses, called jellyfish bloom or smack of jellyfish.
Where are jellies found?
Jellyfish have been in existence for at least 500-700 million years and live all over the world in any sort of water; most species are found in the ocean but some even in freshwater.
They thrive in warm waters but are abundant in the icy Artic too. Usually, they swim near the surface, but have been discovered in the deepest depths too by scientists.
Shallow, warm water coastline areas provide the most excellent conditions for jellyfish – therefore they appear in large numbers at popular tourist destinations in the summertime, and this is when beachgoers, swimmers and snorkelers encounter them and in unlucky scenarios, get stung by them.
What time of the year jellyfish are the most active?
Warm waters provide the best conditions for jellies and their ilk meaning their appearance tends to coincide with the peak tourist season. But this does not mean that you need to avoid beach destinations during the summer months or that you cannot go swimming, just be prepared for accidental contacts.
How do jellyfish sting?
Jellyfish sting with their tentacles for two reasons: when they defend themselves and when they hunt for food. The ‘long arms’ are covered with special cells called cnidocytes. These cells contain specialized structures (nematocysts) working like tiny harpoons; upon contact – or with human skin in our case – they release venom-filled tubes into the prey and the released toxin paralyzes the target.
This toxin is usually strong enough only to paralyze crustaceans or smaller fish so a typical sting only causes red marks, itching, numbness or burning sensation on the skin. An interesting fact is that some jellies can sting despite having no tentacles; the so-called upside-down Cassiopea jellyfish releases a sticky slime full of stingers to trap its prey. If swimming through this cloud, even humans can experience a stinging sensation in the water and later, extraordinarily itching.
How many tentacles does a jellyfish have?
Depending on the species, jellyfish usually have four to eight tentacles, but some have hundreds. Also, the tentacles vary in size too; generally, they reach 1-3 feet/0.3-1m in length but there are species with tentacles up to 100-120 feet/30-36m long such as the Lion’s mane.
Do all jellyfish sting?
Although about 150 million people suffer jellyfish stings each year, there are only certain species that can be harmful to humans. For instance, one of the most common jellies found throughout the world’s oceans, the moon jelly – which is easily recognizable from its purple-colored, translucent body – is completely harmless along with many other species such as the famous Palau’s Golden Jellyfish or the globe-shaped, rainbow-like colored sea gooseberries.
This, however, does not mean that such jellies are non-stinging; in fact, their sting is not strong enough to get through human skin or their venom is so mild that most people do not show any reaction to it.
Jellyfish sting symptoms
In most cases, if you get stung by jellyfish, it will cause just discomfort and localized symptoms on the affected area of the body where the tentacles have contacted the skin.
Common signs of jellyfish stings:
- burning sensation
- moderate stinging pain
What does a jellyfish sting look like?
When a jellyfish stings a person, the released tiny stingers (nematocysts) often leave a visible sign on the skin too that looks like the print of the tentacle. These track marks will get irritated/painful, may give you a burning sensation and the victim will experience redness, itchy rash at the sting site.
How to treat a jellyfish sting?
The treatment of a jellyfish sting always depends on the type of jelly, how extensive the affected skin area is and how one’s body reacts to it. Most stings -although they can cause discomfort- do not require medical care just first aid directly at the beach where the incident happened.
Steps of a mild jellyfish sting treatment:
- Rinse the area with seawater, do not use fresh water
- Remove the visible tentacles with tweezers, a plastic card so that you can avoid contact with bare skin
- Apply a heat pack/hot towel or soak the affected area in warm water for 30-40 minutes – it helps inactivate the toxins and also reduces the pain
Should you have vinegar available, you can rinse the area with that too. Since it is an acid, it neutralizes the unfired nematocysts and can prevent further venom release.
Until the sore does not heal, you may cover it with a thin layer of antiseptic cream to cleanse and prevent infection. To reduce pain, you may take non-steroidal anti-inflammatory drugs.
If you do not have the right accessories with you or you can’t reach the area where you got stung, go to the nearest first aid point or lifeguard station for help.
Does urine help jellyfish stings?
There are various myths associated with jellyfish stings and one of the most common ones is that you should pee on it. This assumption may originate from the fact that urine contains substances like ammonia and urea. If such compounds are used alone, they may help with certain stings, but in human pee, they are diluted in water and found at very low levels, so are not effective.
Instead, urinating on the sting may result in the spreading of the venom over the skin and increases the risk of infection, therefore, the best is to forget about the pee cure.
Author’s note: The same applies to cleaning the wound with alcohol and for rubbing sand on it – You may have seen these techniques in movies, but these would also just spread the venom and cause infection.
How long does a jellyfish sting last?
Symptoms usually remit after a short period of time; pain should last only for a few hours, skin reaction for a few days. If the person’s condition who got stung gets suddenly worse, the skin irritation, redness or pain does not go away or new symptoms develop, medical help may be necessary.
Only in rare cases jellyfish stings cause life-threatening conditions, but those who got stung on very sensitive areas (near the eye, mouth or genitals), have allergies, other underlying conditions or made contact with a dangerous species might develop extreme symptoms.
Should you experience any of these severe reactions or any other complications, seek medical help immediately.
- whole-body rash or redness
- blisters on the skin
- muscle pain
- difficulty breathing
- rapid heart rate
- stomach ache
- increased sweating
- development of deep sore
Factors that determine the severity of the victim’s reaction
The reaction that people have to a jellyfish sting varies individually. Some might not even notice they were getting stung while others react badly so that they need medical help. The main things that determine the severity of one’s reaction:
- the type of the jellyfish
- location of the sting
- the size of the area that came into contact with the tentacles
- how long the body/skin was exposed to the stingers
- the victim’s age and health
Delayed reaction to jellyfish sting
Those who suffer from hypersensitivity – allergic immune reaction – may experience delayed skin reactions. Rash, swelling, itching can occur hours, days but even weeks after the sting and can be followed by weakness, chest pain or fever. Depending on the patient’s conditions, it may be advisable to see a doctor to prevent complications.
Can jellyfish sting when dead?
Jellies’ stingers, the nematocysts are microscopic non-living structures called that only release their toxins when coming in contact with an object. This means that the stinging cells can keep on firing in the tentacles for hours after the jellyfish has died.
Therefore, those that have washed up onshore may still sting even when looking dead so be careful to avoid stepping in one when walking on the beach or wading in the water.
Most dangerous jellyfish in the world
The possibility of encountering dangerous jellyfish is rare while casual beach activities, but they may be out there so it is crucial to be able to identify those species that pose a potential risk to humans.
The Portuguese Man-o-war is not a single jellyfish, but a group of animals compromising of four separate polys. It got its name because its gas-filled uppermost polyp sits above the water and looks like a warship at full sail. These species live mostly in warmer seas and since they float on the surface, they are mostly propelled by winds.
Man-o-war has very long tentacles and a very strong venom, however, it is rarely deadly. Its sting leaves red welts on the skin and can cause respiratory problems and extreme pain.
One of the world’s largest jelly species, Lion’s mane lives in cooler waters in the North Pacific Ocean; it can be found mainly near Alaska and Washington, and in especially large numbers around Ireland. It typically grows up to 1.5 feet (40 cm) but some of them reach 9.8 feet (3m). It’s easy to see why this species was named after the lion; hundreds of long, orange-brownish hair-like tentacles surround its body.
The sting of Lion’s mane is powerful and can be very painful. It is rarely fatal but can cause severe allergic reactions so if you experience swelling, fever, headache, dizziness, breathing difficulties, fever or nausea, consult a doctor.
Chironex fleckeri box jellyfish
Known as sea wasp too, Chironex Fleckeri is a type of box jelly. This species is usually found in northern Australia and in the Indo-Pacific region including the Philippines, Malaysia and New Guinea.
It has a small box-shaped body with long (10ft/3m) tentacles. Its painful venom causes irritated red tracks and excruciating pain, and in extreme cases, can lead to fatality.
Appearing once only in Australian waters but have spread farther to Thailand, Japan, Florida and even to Britain, the Irukandji – a certain box jellyfish – means a growing concern. Its transparent body and small size – about the size of a fingernail – make it difficult to see, and therefore to avoid in the water. A sting by an Irukandji is so special that it even got its own name, Irukandji Syndrome.
The victim may experience first only mild symptoms, but severe pain, muscle and stomach cramps along with vomiting and burning skin sensation, in worse cases cardiac complications are following it generally in 30 minutes to 4-12 hours after the incident.
Although there is no doubt that this species is of the most dangerous in the world, but the good news is that people typically survive its sting when receiving proper treatment.
How to prevent jellyfish stings?
Even though jellyfish populations are increasing globally, swimmers and snorkelers likely do not encounter dangerous ones just species with mild stings or no stings at all, so there is definitely no reason to fear the ocean. Also, here are some great tips to avoid getting stung so your pleasant day at the beach won’t be ruined.
Wear a protective suit (rash guard or wetsuit)
When swimming, snorkeling or diving in areas where stingers may be present, the best way of avoiding getting stung is to wear protective suits. There are special stinger suits available, but your regular UV protection clothing, rash guard or wetsuit – depending on the water temperature – will also do the job.
- lightweight, soft fabric made of 53% Polyester and 47% PBT, chlorine resistant, fast drying, shape-retaining
- high-level protection against jellyfish stingers, sea lice and also against sunburns and damage effect from the sun UV rays
- suitable for all type of water sports activities, including swimming in indoor and outdoor water pools, and sea and ocean waters
For the highest-level of protection, choose long sleeve shirts and pants and wear beach shoes while wading in shallow water. Also, even when only swimming, wear goggles so you can see your surroundings in the water.
Use jellyfish repellent sunscreen
Alternatively, you can use a Safe Sea sting blocking sunblock. This combination product provides protection against UV radiation but also contains special ingredients that keep you safe from jellies by inactivating the stinging cells. Apply it like a normal sunscreen before entering the water.
Check local forecasts
Most popular beach destinations have weather pages that issue daily recommended beaches maps in the peak season which lets you know the state of the area’s beaches including water quality, currents, waves and also, jellies. Sometimes even apps are available to download.
Always check if such forecasts are available and if so, follow their recommendations to find the safest beaches. In not available, get information from lifeguards, local health departments or residents and other beachgoers.
Educate yourself about jellyfish
The appearance of jellies is well predictable. By studying some marine biology, you will not only learn interesting facts about these fascinating creatures but will know what species you can encounter in the area you are planning to swim and when is the jellyfish season.
Also, coastline destinations know when these creatures swarm along the beaches and when it is advisable to avoid entering the water. Often warning signs are placed out with the picture of the jellies that are present in the area along with a short description that suggests if that specific species are harmless or not and what to do if one accidentally gets stung. Study these guides and take a photo of them so you will always have the information on hand when needed.
Why are there so many jellyfish?
Jellyfish numbers are increasing worldwide due to four main factors: climate change, human intervention, overfishing and pollution.
The changing climate -warming sea temperatures, acidification – also supports jellies to reproduce more quickly. Unlike most marine creatures, they aren’t vulnerable to warm water temperatures, low oxygen or high acidity levels but thrive in such conditions.
Man-made structures and human activity-related objects such as maritime shipping vessels, docks, oil and gas production platforms also benefit the reproduction of jellies; the larvae need to hook on a solid surface where they stay for several weeks-months and grow into another stage of their life; with the increasing number of such objects in our waters, more and more larvae make it into adult jellyfish.
Due to bad fishing practices, fish are being removed from the water at a rate greater than the population can replenish itself. The use of commercial fishing nets increased the rate of bycatch too when non-target marine species such as turtles and dolphins are caught too. Due to these bad fishing practices, their natural predators disappear so jellies can bloom.
Agricultural and urban and pollution such as fertilizers and sewage and run off the land and end in the sea making the level of nutrients in the water high. Such conditions allow plankton and algal bloom and decrease the oxygen level killing fish and other marine animals but creating a favorable environment for jellyfish.
Millions of jellyfish are living in our oceans and their numbers are rapidly increasing, but there is no need to be afraid if you encounter one along the coast or in the water. Most jellies beachgoers encounter have no strong venom and their sting causes only skin irritation, redness and mild pain but with the appearance of dangerous species beyond their usual habitats, it is essential to know how to identify a sting and what is the best treatment for it. Learning what species can be present in the area where you live or travel to and wearing long-sleeve protection suit while in the water can lower the risk of getting stung.
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