Updated 17 May 2017

Could you be allergic to seawater?

A dip in the ocean is not such a cooling experience if your swim is always followed by an itchy rash. Could it be that you have a seawater allergy?

Getting a rash after exposure to ocean water is quite common, according to the Amercian Academy of Allergy Asthma and Immunology (AAAAI).  However, a sea water or salt water allergy is unlikely say specialists.

Associate Professor Jonathan Peter, head of the Allergology and Clinical Immunology division at UCT’s Department of Medicine and the Allergy clinic at the UCT Lung institute, says that contact with seawater can be both good and bad for allergies.

Read: Seawater spray may cure colds

“Studies have shown benefits of saltwater (saline) nasal irrigation for allergic rhinitis sufferers,” Prof Peter says. There is however a small group of people who develop hives on contact with seawater or cold temperatures.

What is hives?

Hives or urticaria is a raised, itchy rash that appears on the skin, often accompanying allergic reactions. According to Prof Peter, specialists define a reaction to seawater as aquagenic (water) induced urticaria or cold-inducible urticaria. Studies demonstrate the salt content of water can also influence seawater’s ability to produce hives in certain patients.

Antihistamines can be used to prevent hives or to reduce symptoms in many cases. In a few extreme cases, patients must avoid water altogether to avoid developing anaphylaxis. Fortunately such severe cases are rare.

Read: Anaphylaxis

“In cold-induced urticaria, patients will normally have a threshold temperature below which they will develop hives, and some people have been force to relocate to warmer climates to treat their condition,” Prof Peter says.

'Something fishy'

“There are also a number of stinging fish in the sea that can cause skin and even toxic systemic reactions,” he adds.  A common example would be blue bottles found on the South African coastline.

Patients can also be allergic to shellfish or fish, in which case their bodies will make allergic antibodies (IgE) against certain shellfish or fish proteins. Symptoms of these allergies are usually triggered by ingestion, or in some cases, when someone directly handles shellfish during food preparation.  

Despite the fact that the ocean is filled with shellfish, seawater allergies and shellfish allergies are in no way connected, according to Prof Peter. Therefore patients who are allergic to shellfish don't have to worry about swimming.

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Dr Morris is the Principal Allergist at the Cape Town and Johannesburg Allergy Clinics with postgraduate diplomas in Allergology, Dermatology, Paediatrics and Family Medicine dealing with both adult and childhood allergies.

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