Some could have reactions to sunlight or when exercise is combined with certain food
When Melissa (not her real name) excused herself from a university orientation game by saying she was allergic to sunlight, she did not receive much sympathy from her peers.
"Some joked that I was a vampire, but I wasn't amused," said the entrepreneur, now in her late 20s. "I would develop an uncomfortable rash on my neck and back if I am out in the sun for too long."
She usually carries with her sunscreen and antihistamines - medication to ease her symptoms. Ultraviolet rays from the sun can cause chemical alterations in the skin cells, resulting in allergic reactions.
Although Melissa's case sounds unusual, doctors in Singapore have helped patients with allergies to things such as grass, exercise and even chocolate. They may have trouble breathing, break out in painful and itchy rashes, or develop headaches or nausea. In some cases, the reactions can be life-threatening.
But identifying an unusual allergen can be very challenging, according to Dr Elizabeth Tham, consultant at the division of paediatric allergy, immunology and rheumatology at National University Hospital. "(It) requires us to think like a detective and to think outside the box."
For some people, an allergic reaction is caused when exercise is combined with a specific food, such as wheat, shellfish and peanuts.
Once, a teenage boy who had played basketball right after consuming prawns for dinner was taken to the emergency department with hives, facial swelling, throat tightness and wheezing, said Dr Tham.
It was later discovered that he had a rare condition called food-dependent exercise-induced anaphylaxis. Anaphylaxis is a serious allergic reaction that occurs quickly and can be fatal.
The boy had never had an allergy to either seafood or exercise, but the anaphylactic reaction resulted from a combination of the two.
But such an allergy can go unrecognised or underdiagnosed, said Dr Tham. "It is often difficult to diagnose as many people may experience similar symptoms during exercise, such as when they are unfit or have an asthmatic attack."
Doctors advise these patients to avoid known food triggers a few hours before or after exercise.
Often, patients have to make drastic lifestyle changes. Someone who develops rashes after a brief exposure to sunlight, for instance, may have to wear long sleeves and sunscreen throughout the day.
Dr Karen Choo, associate consultant at the department of dermatology at Singapore General Hospital, said: "Avoidance of the trigger factors may sometimes require changes to a patient's behaviour and ability to function."
Yet, some allergies can be hard to avoid, "hence most of these patients will have to rely on medication almost daily for symptom relief", said Dr Elaine Loh, a family physician at Dr Tan and Partners @ Scotts.
In some cases, those who have experienced a reaction "may try to continue exposing themselves to the allergen to 'test' if they still develop reactions, or try and allow their body to get used to it", said Dr Tham.
"This is very dangerous and may lead to life-threatening reactions, and is highly discouraged."
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