Author: Dr Lydia Chan, Dermatology Registrar, Dermatology Department, Auckland District Health Board, Auckland, New Zealand. DermNet New Zealand Editor-in-Chief: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy Writer: Gus Mitchell. September 2017.
Various syndromes that may affect the skin have been described after ingestion of fish or fish products. These include:
A combination of the above can occur in the same patient. It can be difficult to differentiate the cause, as symptoms may appear similar.
Scombroid fish poisoning is caused by eating decomposing scombroid fish, such as kahawai, mackerel and tuna. Bacteria in the decomposing fish produce various by-products including scombrotoxin, which contains histamine.
The clinical features of scombroid fish poisoning include:
Scombroid fish poisoning resolves without complications. In severe cases, symptoms may persist for several days.
Scombroid fish poisoning is usually diagnosed from a clear history of onset of symptoms within one hour of eating a particular fish.
Scombroid fish poisoning can take minutes to induce a reaction. Other reactions due to fish ingestion tend to progress more slowly, over hours, days or weeks.
The treatment of scombroid fish poisoning is rapid-acting oral antihistamines, which may resolve the symptoms within minutes.
The responsible decomposing fish should be discarded.
Scombroid fish poisoning rapidly resolves. Patients can eat the same species of fish again, as long as it is stored in cold conditions to prevent bacterial decomposition.
Vibrio vulnificus infection can follow consumption of contaminated seafood such as raw oysters. This infection may also contaminate open wounds exposed to warm seawater.
The clinical features of a Vibrio vulnificus infection due to eating contaminated seafood include:
Patients with Vibrio vulnificus infection may become very unwell and require hospitalisation.
Vibrio vulnificus infection can be suspected in unwell patients if they have a history of eating contaminated seafood.
The bacteria can be isolated from blood, stool and/or wound cultures using a special medium.
The differential diagnosis for Vibrio vulnificus infection includes:
The outcome of Vibrio vulnificus infection is usually good with prompt treatment. The infection may be fatal in up to 50% of patients that have pre-existing liver disease. It has been recommended that patients with liver disease do not eat raw shellfish.
Mercury poisoning is due to ingestion of mercury, including mercury in fish. In New Zealand, high mercury levels are found in the following species of fish:
The clinical features of mercury poisoning tend to occur weeks to months after acute ingestion. Symptoms may include:
Skin signs may include colour changes in the hands and feet, with associated pain and itch. Hair loss and nail loss has been described. Excessive sweating and inflammation of the gums may occur.
Complications of mercury poisoning include pain and colour change in the extremities and permanent loss of teeth from gum inflammation. Hair and nail loss may be slow to resolve.
If severe, patients may develop acute renal failure.
Mercury poisoning can be diagnosed from measuring levels of mercury in the blood.
The differential diagnosis for mercury poisoning is broad, as symptoms may be nonspecific.
The treatment of mercury poisoning includes supportive care, such as correcting any fluid and electrolyte imbalances.
Chelation with meso 2,3-dimercaptosuccinic acid may be used to prevent methylmercury uptake by erythrocytes (red blood cells) and hepatocytes (liver cells).
It is essential to avoid further exposure to mercury. Avoid eating the aforementioned fish species. Be aware that various herbal and traditional remedies may contain mercury.
Signs and symptoms of mercury poisoning gradually disappear once treatment is started, providing there is no further ingestion.
Acute vitamin A toxicity is caused by the ingestion of too much vitamin A. There are high levels of vitamin A in fish liver of various species, including:
Vitamin A toxicity can also be due to:
Acute vitamin A toxicity results in redness of the skin, followed by desquamation (peeling), dryness and peeling of the lips, and dry eyes. Hair loss and nail thinning or loss may become apparent after some weeks.
Other features of vitamin A toxicity include headache, abdominal pain, nausea and vomiting.
Severe overdose of vitamin A can lead to death.
Intake of high levels of vitamin A or other retinoids during pregnancy have been associated with birth defects.
Diagnosis of vitamin A toxicity is based on the patient’s signs and symptoms, and a history of ingestion of vitamin A or a retinoid. There is a poor correlation between toxicity and serum retinol levels, as it Vitamin A is rapidly metabolised to retinoic acid. Blood samples must be stored in the dark before analysis.
The differential diagnosis for vitamin A toxicity is broad, as symptoms may be nonspecific. When symptoms are associated with ingestion of fish, consider:
The source of vitamin A should be avoided, including fish and various supplements, herbal or traditional remedies containing vitamin A.
Vitamin A will be processed by the body over time. Fluid and electrolyte abnormalities due to vomiting should be corrected.
The outcome of vitamin A toxicity is good. Skin peeling settles over a few weeks as new skin cells are generated.
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