The unpredictable nature of shellfish allergies was brought to the fore in an incident in Singapore, Malaysia, where a 60-year-old woman died due to an allergic reaction after eating prawns.

According to reports, Khoo Siew Hong ignored the fact that she was allergic to prawns and went ahead and feasted on a couple from a dish of laksa (spicy noodle soup) on March 8.

The allergic reactions started a few hours later, and she was rushed to hospital where she died some time later.

According to the state coroner’s report released Monday, Khoo's death was stated as a "truly unfortunate misadventure."

"Allergic reactions to prawns and other shellfish can be unpredictable, with varying symptoms between different individuals. A single individual may not always experience the same symptoms during every reaction, which may have lulled Ms Khoo into a sense of complacency that such episodes could readily be addressed and controlled. Often, the allergic reactions become more severe with each exposure,” the coroner said, Strait Times reported.

Shellfish allergies are tricky in the sense that people may develop them at various points during their lives; and once they get it, it tends to recur during the rest of their lifetimes, Healthline reported.

Incidentally, the same type of seafood that one might have consumed with no issues in the past might without warning become the trigger for allergies.

Most people who develop allergies to a specific kind of seafood are also allergic to other types too. This is the reason doctors recommend patients with seafood allergies to stay away from all types of crustaceans and molluscs even though they might not be equally allergic to some kinds of seafood. 

Prawn Despite having a prawn allergy Khoo Siew Hong ate a couple of pieces of prawns a from a traditional seafood delicacy called Laksa. In this photo, a bowl of $3.40 laksa is seen at Roxy Laksa stall at East Coast Lagoon Food Village in Singapore July 30, 2016. Photo: Reuters/ Edgar Su

According to Food Allergy Research & Education, an estimated 6.5 million American adults suffer from seafood allergies, which is the most common among adult-onset food allergies.

Unlike other kinds of allergies, shellfish allergies tend to grow more severe with each exposure. Some of the symptoms of seafood allergies that can start within minutes of consuming some type of seafood, are tingling in the mouth, abdominal pain, nausea, diarrhea, or vomiting, congestion, trouble breathing, or wheezing, skin reactions including itching, hives, or eczema, swelling of the face, lips, tongue, throat, ears, fingers, or hands, lightheadedness, dizziness, or fainting.

When the condition turns from bad to worse, a person with seafood allergies goes into anaphylactic shock, accompanied by a swollen throat that causes shortness of breath, rapid increase in pulse rate, extreme dizziness or loss of consciousness and a severe drop in blood pressure. Under such circumstances, the allergic individual is recommended to immediately seek professional help to minimize the risk of death.

Khoo, who was unemployed and used a wheelchair to get around, went to Shin Yeh restaurant in Liang Court shopping mall for lunch four days before her death. There she safely ate a few prawn dumplings without any consequences, according to the Strait Times report. 

Hence, she again tried a couple of pieces of prawns a few days later in the afternoon. After a couple of hours she started feeling itchy in her throat. An antihistamine tablet, prescribed to her by a doctor, was didn't help.

Khoo's face started to develop a rash and was swollen slightly; she was soon complaining of difficulty in breathing.

The Singapore Civil Defence Force was contacted following the worsening of her reaction and cardiopulmonary resuscitation was conducted on her following instructions received from the emergency services.

When this didn't work, Hong was rushed to the Tan Tock Seng Hospital and given 12 doses of adrenaline after her body went numb. However, Hong did not regain consciousness again. She was pronounced dead by the hospital later in the evening.