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Microscopic Sea Lice

Have you ever been swimming in the ocean and felt like you've got an itchy bite? Forgot to wear a stingersuit? Did you come out in a rash after swimming in the ocean? The chances are it is the result of what's commonly called sea lice, tiny stingers that get stuck in your swimwear or arm pits.

In fact, it's not 'sea lice' in the way fishermen might think of it. The marine parasite that affects fish actually has nothing to do with the itchy rash you've experienced.

The 'sea lice' that causes the 'itchy bites' are actually tiny little jellyfish or stinger larvae that have the same stinging cells (nematocysts) as an adult jellyfish/stingers, but because they are only small they only affect a small area.

They tend to travel in large groups or 'blooms' and will be prevalent in warm summer waters. Some ocean swimmers suggest you'll encounter them when there's lots of seaweed floating around.

Know if you have been in contact with sea lice

They are microscopic in size and transparent in water so you've got no chance of seeing them. The first you'll know about it is when you start to itch.

You'll get the worst of it where the larvae get trapped under your togs or rashie, or even your armpit where they feel trapped causing the stinging cells to fire.

Get rid of sea lice

The worst thing you can do is itch them, you're best to just flush your skin in fresh water when you get out, preferably with your swimsuit removed.

When drying yourself off use a patting motion rather than rubbing the affected area.

For the majority of people the itch will be the worst part, and it could be delayed and last for a few days to a week after.

For some people it could get worse with a severe reaction in which case you should seek further medical assistance.

Give your swimsuit a good wash before you wear it again just to make sure all the cells have been washed out. If you're looking for relief treatment try vinegar, various itchy bite rash creams or antihistamines, but check with your doctor first.

There are two types of sea lice

The first type of sea lice is a parasite that feed off fish. They do not affect humans and are not a cause for concern to swimmers and divers.

The type of sea lice that is a concern for humans is the type produced by jellyfish and other sea creatures that sting. They produce a minuscule larva which contain a sting that can cause a very unpleasant reaction when it comes into contact with your skin.

The Thimble jellyfish is thought to be the main producer of sea lice. They are very small but can be seen with the naked eye, but are almost impossible to see when they are in the water.

They are known to thrive and infest the warmer waters off the Gulf of Mexico, the Caribbean and along the east and west coasts of America throughout the hotter summer months.

Sea lice effect on your skin

This tiny sea lice gets caught up between the material of the bathing suit and the body, or in places like under the arms. Their inbuilt reaction to becoming trapped is to release their sting into the body.

As with any type of sting, some swimmers may have a severe allergic reaction and will require immediate medical attention. However, the majority of people will experience an excruciating itch with a red rash and blisters appearing on the affected areas of their body. Younger children may also experience fever, nausea, vomiting, chills and headaches.

Symptoms may not fully develop for up to six hours after being stung and can last from anything from two days to two weeks. The rash and blisters will become very itchy, but scratching can cause an infection if the blisters burst. Particularly, with younger children take every precaution to prevent them from scratching.

Sting Prevention

If you are aware of a sea lice problem in the area, wear a full body swimsuit or wetsuit, especially when diving.

Even though sea lice are known to slip in between the swimsuit and the body, this can be prevented or minimised by wearing a stinger suit or sunsuit which fits like second skin if worn tight.

These suits are known to protect against jellyfish stings, and provide all day protection against the sun UV radiation.

After swimming or diving always take off your swimsuit and shower thoroughly. This helps reduce the odds on you being stung by larvae trapped in your swim clothes.

Wash your swimsuit thoroughly before you use it again.

Wear fresh swimming clothes when you go into the hotel pool or spa. Don't bring in anything from the sea.


Applying some vinegar can help to relieve the itching. Alternatively, use a hydrocortisone cream, oral antihistamines and an antibiotic cream to reduce the itching and prevent infection.

You should adhere to the advice given by a pharmacist on the application of these creams, especially if you suffer from any allergic reaction to such creams. They may not always be suitable for the young or the elderly so be sure the read the instructions carefully.

There are commercial products that can be rubbed into the skin to act as a deterrent to this parasite. However, as with most things these will not work for everyone.