Do not exercise immediately after eating.

This is common advice, but it means life or death for a small group of people who suffer from food-dependent exercise-induced anaphylaxis.

The condition means that any form of exercise done after eating a food they are sensitive to will trigger off a potentially deadly reaction.

In Singapore, at least five people have been known to suffer from this rare condition, reported Shin Min Daily News. Of the five, three are male and the rest, female.

They were diagnosed between August 2006 and July 2008. During these two years, the five - aged between nine and 20 - had separately shown severe allergic reactions when they exercised after a meal and had to be admitted to a local hospital for emergency treatments.

Symptoms displayed included urticaria, or hives, hypotension and breathing difficulties. Two of the patients also reportedly lost consciousness.

The five had exercised 15 minutes to 21/2 hours after eating shellfish.

Exercise-induced anaphylaxis

Anaphylaxis is a very severe allergic reaction that affects the entire body.

This life-threatening condition may occur minutes to hours after exposure to an allergen.

The person may have skin rash or hives, a rapid, weak pulse, and nausea or vomiting.

MayoClinic.com reported that the massive amount of chemicals released by the immune system during anaphylaxis can cause one to go into shock; airways narrow and breathing becomes difficult, while blood pressure drops suddenly.

If left untreated, death may result.

Anaphylaxis can be triggered off by exercise. This condition, known as exercise-induced anaphylaxis (EIA) can cause the person to experience hives, itching, shortness of breath, and low blood pressure, usually five to 30 minutes after they begin exercising.

Jogging is the most common type of exercise that triggers off EIA, notes a medical doctor in About.com.

Some people experience EIA symptoms if they eat something they are sensitive to less then 24 hours before exercising. Called Food-dependent EIA, this condition occurs only if the person exercises after eating a food they are allergic to. The food or exercise alone does not produce symptoms, notes BBC.

Prompt treatment for anaphylaxis is critical as it can result in death. In order to prevent EIA symptoms, doctors advise people to avoid exercising alone and to only exercise on an empty stomach.

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