As with every summer, swarms of jellyfish appeared along Israel's coastline this year as well, led by the nomad jellyfish, the most common stinging species in our region. However, this time they arrived early: Observations of exceptional quantities were already received at the beginning of May, and during late May and early June, reports multiplied from the northern beaches down to Ashkelon.
The report map of the "Jellyfish in Israel" project indicated late last weekend that nomad jellyfish were present on many beaches, sometimes in quantities of dozens or even more. Even when a whole jellyfish is not visible in the water, tentacles that detached from it and microscopic stinging cells may remain active and cause a burning sensation.
Year after year
The nomad jellyfish is an invasive species originating from the Indian Ocean and Red Sea region. It penetrated the Mediterranean Sea through the Suez Canal, in a process known as Lessepsian migration, and was first documented on Israel's coast in the 1970s. Since the mid-1980s, its summer swarms have become a permanent seasonal phenomenon, and it subsequently spread to other parts of the Mediterranean.
The appearance of the jellyfish in June is not accidental, but it is also not the result of an organized journey by a swarm making its way every year from a distant place to the shores of Israel. The life cycle of the nomad jellyfish includes a tiny stage fixed to the seabed called a polyp. The polyps survive during the winter, and when the seawater warms up in the spring, they begin to reproduce and release young jellyfish.
The sea temperature is only part of the picture. The exact location of the swarms is also determined by sea currents, wind direction, wave height, and the structure of the beach. A wind blowing from the sea toward the land can bring jellyfish and tentacle fragments closer to the bathing area, while winds and currents in the opposite direction may distance them. This is the reason why dozens of jellyfish may be found on one beach, while on an adjacent beach they will hardly be felt.
Jellyfish have a certain independent swimming capability, and they do not drift completely passively. A study conducted at the University of Haifa showed that nomad jellyfish are capable of adjusting their swimming direction to the current and even swimming against it under certain conditions. Nevertheless, when dealing with large swarms, the currents and winds are what largely determine whether the jellyfish will be found in the deep sea or near the shore.
The warming of seawater may extend the period during which conditions are suitable for the reproduction and development of the nomad jellyfish. Studies from recent years have found that temperature affects polyp survival, their reproduction, and the release of young jellyfish.
Other factors may contribute to the spread of jellyfish swarms, including changes in the ecosystem, food availability, fishing, pollution, and the construction of marine structures upon which the polyps can settle. However, there is no single factor that alone explains the intensity of the swarms each year, and it is not yet possible to accurately predict the size and path of each swarm.
The nomad jellyfish season on Israel's coast usually reaches its peak in June and July. In most years, the main swarm begins to weaken during the second half of July or early August, but there is no fixed date on which the jellyfish disappear.
A change in the direction of the winds or currents can clear a specific beach of jellyfish within days, and then bring them back. Even after the large swarm distances itself, individual jellyfish and stinging cells may remain in the water. Other species of jellyfish can also appear on Israel's coast in the autumn and winter.
Therefore, as of early June 2026, it is too early to determine on which day the current swarm will end. Based on the known seasonal pattern, a significant presence of nomad jellyfish is expected to continue at least through June and part of July. The condition of the beaches can change daily, so it is recommended to check lifeguard reports and the updated jellyfish map before bathing.
Neither vinegar nor alcohol
And this is how the sting works: On the jellyfish's tentacles are stinging cells called nematocysts. In each cell is a sort of microscopic needle, which fires rapidly following contact or stimulation and injects venom into the skin.
The common reaction includes a burning pain, redness, local swelling, itching, and whip-like or stripe-like marks on the skin surface. The pain may last from minutes to hours, while the redness and itching can remain for several days. Sometimes a delayed skin reaction develops even after the initial injury has already calmed down. There is no need to touch a whole jellyfish to get stung. A tentacle detached from its body, a dead jellyfish washed ashore, or stinging cells left in the water may also continue to release venom.
What to do immediately after a sting? First, one must get out of the water, especially if the pain is strong, if it is a child, or if there is weakness or dizziness. Do not rub the skin, scratch it, massage it, or wipe it forcefully with a towel, because these actions can cause further activation of stinging cells left on the body surface.
If visible tentacles remain on the skin, they should be removed gently using a rigid object, a plastic card, a stick, or a gloved hand. Do not touch the tentacles with bare hands. According to Ministry of Health guidelines, an initial rinse can be performed with seawater. Afterward, you can rinse for a few minutes under a direct stream of fresh water, without rubbing. Do not submerge the area in a bowl and do not repeatedly pass a cloth or sponge over the skin.
To relieve the pain, you can apply a cold compress or an ice pack wrapped in cloth for short periods of time. Do not apply ice directly to the skin. A pain reliever can be used, such as paracetamol, Acamol, or Dexamol, or ibuprofen, Nurofen, or Advil, depending on age, weight, background diseases, and the instructions for use.
What is forbidden to do? Do not pour vinegar on a sting caused by a nomad jellyfish. In laboratory experiments, it was found that vinegar may encourage further release of venom from the stinging cells of this species and worsen the injury. Vinegar is used in some global guidelines against certain species of box jellyfish, but the recommendation is not sweeping for all jellyfish and certainly not for the nomad jellyfish common in Israel.
Do not pour urine, alcohol, soft drinks, disinfectants, or other household substances on the skin. Do not apply sand and do not scratch the area with a card or a razor blade when tentacles are still visible on it. These actions can wound the skin or activate additional stinging cells. There is no need to routinely apply Silverol or an antibiotic preparation on every sting. Most injuries are not deep burns and do not become infected. Treatment with burn ointments or topical antibiotics should be given according to the appearance of the injury and upon the recommendation of a doctor or pharmacist.
You must immediately contact MADA at telephone 101 or seek medical treatment if shortness of breath, wheezing, swelling of the lips or tongue, difficulty swallowing, hoarseness, fainting, confusion, extreme weakness, repeated vomiting, chest pains, or a widespread rash appear.
Urgent attention is also required after an extensive sting, injury to the face or eyes, pain that does not decrease, multiple blisters, significant swelling, or general deterioration. Young children, the elderly, and people with heart disease, lung disease, or a history of severe allergic reactions may require an earlier evaluation.
Anyone who carries an adrenaline injector due to a life-threatening allergy and has developed signs corresponding to a severe allergic attack called anaphylaxis (skin allergy or swelling of the lips or tongue with shortness of breath, with a drop in blood pressure, or loss of consciousness or vomiting or diarrhea) must use it according to the guidance they received, and immediately call MADA. Even after injecting adrenaline, medical supervision is required. In case of injury to the eyes, do not rub them and do not rinse under high pressure. Perform a gentle rinse and arrive as soon as possible for an examination by an ophthalmologist or to an emergency room.
The author is a specialist in pediatrics, a sports and aviation physician, and the medical commentator for Maariv