# Jellyfish dermatitis

Jellyfish dermatitis is a cutaneous condition caused by stings from a jellyfish.$^{:430}$

## Immune response to jellyfish stings in humans

Jellyfish stings can trigger a complex immune response in human skin similar to the response to pathogens or allergens. When jellyfish venom, carried by the stinging cells of the animal (nematocysts), comes into contact with the skin, it interacts with various cells and substances in the body. These interactions involve keratinocytes, tissue macrophages, dendritic cells, and mast cells, which are key players in the immune system.
Keratinocytes, which form the outer layer of the skin, not only act as a physical barrier but also release a protein called thymic stromal lymphopoietin. This protein activates T-cells to produce cytokines, which are known to be involved in allergic skin reactions.
Dendritic cells, a type of immune cell, capture and present antigens (foreign substances) to T-cells, or they migrate to lymph nodes to initiate immune responses. They contribute to the immune response to jellyfish venom and it's components through various receptors involved in recognizing pathogens.
Mast cells, which are abundant in the skin, play a significant role in inflammation. When stimulated, they release various substances that promote inflammation, such as histamine, platelet activating factor, prostaglandins, leukotrienes, proteases, and cytokines. Mast cells can be activated in three ways during a jellyfish sting: directly through the venom's bioactive substances, through the interaction with components of the jellyfish stinging cells, or through physical changes at the sting site.
In the case of repeated jellyfish stings, an allergic response mediated by a type of antibody called IgE may also contribute to mast cell activation and the release of mediators in response to specific substances bound to their surfaces. This could lead to more severe symptoms.

## Symptomatology

The symptomatology of jellyfish stings encompasses a variety of reactions experienced by individuals who come into contact with these aquatic creatures. In a comprehensive study conducted across three Marine stations, it was observed that an alarming 79% of fishermen reported a history of being stung by jellyfish. The most commonly affected areas were the hands and arms, followed by the legs. Stings were found to elicit rapid skin reactions, typically manifesting within 5 minutes. Fishermen frequently complained of itching, a burning sensation, and the appearance of erythematic wheals. Interestingly, a notable delayed type of skin reaction emerged a few days after the initial sting, with 62% of cases developing painless and itchy erythematous monomorphic papular rashes at the site of the sting. Encouragingly, these reactions generally resolved on their own over time.
Local remedies were commonly employed by the fishermen to alleviate the symptoms associated with jellyfish stings. Seawater, tap water, and ice were among the frequently utilized remedies. Some fishermen considered jellyfish stings to be of minimal significance and did not deem it necessary to seek medical assistance.

## Remedies and treatment

Jellyfish stings have been the subject of much discussion, with numerous homemade remedies circulating among the general public. However, it is crucial to separate factual recommendations from myths when it comes to treating these stings. One factual recommendation is promptly removing the jellyfish tentacles, as they can continue to release toxins even after detachment. Using a plastic object like a credit card to brush off the tentacles effectively removes them, while vigorously rubbing the skin can exacerbate the irritation by increasing toxin release.
Contrary to popular belief, immersing the wound in cool fresh water may worsen symptoms by increasing toxin release. Instead, rinsing the affected area with seawater is advised to remove as much of the tentacles as possible. Baking soda has shown effectiveness against certain jellyfish species in in-vitro testing, but its efficacy may vary depending on the species involved. Household vinegar, containing acetic acid, can provide relief for jellyfish envenomation, particularly for species like the Australian box jellyfish and Hawaiian box jellyfish. However, its effectiveness may be limited for other species. Vinegar blocks the release of toxins from specific species but does not comprehensively treat established envenomation effects. Vinegar has been known to increase the nematocyst discharge in Portuguese man o' war (P. physalis) and the Atlantic sea nettle (C. quinquecirrha).
Dispelling a popular myth perpetuated by the television show Friends, using urine on a jellyfish sting is not only a myth but can also be dangerous. In-vitro studies indicate that human urine can trigger toxin release and increase pain caused by various jellyfish species. The most effective measure for treating a jellyfish sting is immersing the affected area in a hot bath with water temperature between 40 and 45 °C (104 and 113 °F) for approximately 20 minutes. Heat alters the protein structure of the jellyfish venom, providing significant pain relief. Additionally, it is important to protect the affected area with total sunblock sunscreen for at least two weeks to prevent permanent skin darkening resulting from the inflammatory reaction.
While these remedies can provide initial relief, seeking medical attention is advisable after a jellyfish sting. A healthcare professional can offer supportive measures to control pain and reduce inflammation. Immediate medical attention is particularly important if symptoms such as shortness of breath, wheezing, flushed skin, and dizziness occur. Informing the doctor about the jellyfish sting is crucial for proper evaluation and treatment.

## Prevention

It is now possible to purchase sun block that could prevent or decrease symptoms of stings. Wet suits and foot wear can also be protective. Avoid swimming in areas in which you can see jellyfish in the water. Check about any warnings prior to entering the water. Do not handle dead or beached jellyfish on the beach.

## Examples of jellyfish species that sting

Injuries to humans are the result of about 100 of the 9000–10,000 Cnidarian species.
* Atlantic sea nettle (Chrysaora quinquecirrha)
* Australian box jelly (Chironex fleckeri)
* Black sea nettle (Chrysaora achlyos)
* Carybdea species
* Chironex yamaguchii
* Compass jellyfish (Chrysaora hysoscella)
* Four-handed box jellyfish (Chiropsalmus quadrumanus)
* Irukandji jellyfish (16 species)
* Lion's mane jellyfish (Cyanea capillata)
* Mauve stinger (Pelagia noctiluca)
* Nomad jellyfish (Rhopilema nomadica)
* Nomura's jellyfish (Stomolophus nomurai)
* Pacific sea nettle (Chrysaora fuscescens)
* Portuguese man o' war (Physalia physalis)