The Bottom Line: Can you develop allergies as an adult?
SINGAPORE – After his heart surgery in 2021, Mr Edwin Sim felt some itchiness on his wrists and ankles.
“I thought my skin was sensitive to the adhesive tapes used to secure the tubes on me,” says the 48-year-old learning consultant, who is married with two children.
Patches of red bumps later formed all over his body, including his lips, arms, chest and thighs.
He was told he had hives – a raised, itchy rash that appears on the skin. He also suffered from anaphylaxis, a life-threatening reaction in which blood pressure drops and breathing is restricted.
It turned out that he was allergic to the antibiotic cefazolin.
Mr Sim’s doctor had to administer adrenaline intravenously to improve his blood pressure levels. He was also given topical wipes to help relieve the itch.
It seems like a clear case of an adult-onset allergy, but it could also be that Mr Sim was always allergic to the antibiotic but had never been exposed to it. It is not always possible to tell.
While doctors say there are cases of people developing allergies in adulthood, this is not very common.
An allergic reaction happens when a person’s body overreacts to an external element by producing an antibody called immunoglobulin E, or IgE.
When this occurs, the body releases histamine, a chemical that triggers symptoms such as itching, sneezing, wheezing and swelling. In severe cases, it may cause anaphylaxis.
In her late 20s, Ms Sheryll Wee started sneezing and having watery eyes whenever she was in a dusty environment. Previously, she had no such issues.
The 32-year-old retail assistant went to a doctor and was told she had allergic rhinitis, a condition in which the nose gets irritated by something one is allergic to – such as pollen, dust or pet dander – causing symptoms such as sneezing and an itchy nose.
As a result, she had to use an anti-dust mite pillow and mattress cover, wash her bedding every week and vacuum her house regularly.
There are several reasons allergies develop in adulthood.
Dr Jonathan Tan, a family physician at Silver Cross Family Clinic, says a family history of allergies may put you at a higher risk of developing allergies some time in your life.
“In some cases, you may already be predisposed to a certain allergy, but have never been around that allergen much during childhood,” he adds.
For example, you may be allergic to pet dander, which is composed of tiny bits of skin shed by cats, dogs, birds and other animals with fur or feathers, but never had pets growing up.
So if you decide to get a dog one day, the sudden exposure to high levels of dog dander may trigger an allergic reaction that has never happened before, he explains.
On the other hand, says Dr Zeng Shanyong from Dr Tan & Partners Clinic, repeated exposure to allergens over a long period of time can cause the immune system to overreact and increase one’s risk of developing an allergy.
He once saw a young woman with allergic rhinitis after she got a new pet cat. Her office had four cats, and she was doing fine until the arrival of her new kitty at home.
“A blood test showed that the patient had raised levels of IgE to cat dander. It was likely that she had sensitisation to cat dander all along, but her symptoms worsened with prolonged exposure to a cat at home,” says Dr Zeng.
He says allergic sensitisation is the development of antibodies to allergens that are ingested, absorbed or inhaled.
For some people, once these allergens are exposed to the lining inside the airway, it triggers changes within the immune system.
When people with sensitisation are re-exposed to these allergens, it can trigger a release of antibodies into the circulation and activate mast cells (a type of white blood cell) and basophils (a type of immune cell), which can provoke an allergic reaction.
Dr Tan saw a hairdresser who developed a severe allergy to hair dyes and chemicals after working in the industry for more than 30 years. The patient, who is in his 50s, suddenly had hands that were festering, excoriated, red, itchy and painful.
“We went through his history but couldn’t identify what caused the change in the last one year that prompted such a reaction. It could have been an allergic reaction to a new product or technology used in his line of work,” he says.
He suggested that the patient experiment with different types of gloves, such as latex, non-latex or powdered ones, or using an applicator to handle hair dyes or chemicals instead of his hands.
“I still see the patient sometimes when he has skin flare-ups during festive periods such as Chinese New Year, when there are more customers,” adds Dr Tan.
Dr Tricia Chong, a consultant at National Skin Centre, says as people age, there is a reduction in epidermal lipids in the skin.
The weakened skin barrier may allow an increased penetration of allergens, which can cause allergic contact dermatitis, an inflammatory disease of the skin. The risk of the disease is increased by cumulative exposure to allergens with age.
There are also cases in which adults with no history of food allergies unexpectedly develop them later in life.
A possible explanation for this, says Dr Tan, is a cross-reaction to other allergens, such as the pollen-food allergy syndrome.
This occurs when a person has an existing allergy to a particular pollen. Due to the similarity between the pollen’s protein structure and a particular food protein, the immune system may mistake the food protein for a pollen allergen and trigger a reaction, he explains.
As the allergen enters through the mouth, itching and swelling may result and spread to the person’s entire face.
According to a study published in peer-reviewed journal Environmental Health Perspectives in 2005, people with birch pollen allergy can have an allergic reaction to celery and apples due to the similarity in the protein structures.
Those allergic to grass pollen may also be allergic to melons, oranges and tomatoes.
Changes in the immune system as people age can also cause allergic reactions to come about, says Dr Zeng. As a result, what used to cause a slight reaction may now result in severe symptoms.
Ms Serena Foo used to experience some itchiness in her ears and throat after eating prawns as a child.
“I didn’t think much of it at the time because it was a very mild reaction that went away within one to two hours,” says the 43-year-old, who is married with three children.
In her 20s, she suffered a severe allergic reaction after eating a hotplate beancurd dish that contained prawns.
In half an hour, she developed angioedema of the eyes, which is the swelling of the deeper layers of the skin caused by a build-up of fluid. She also had laryngeal oedema, a condition in which the airway becomes narrowed, making it difficult to breathe.
Ms Foo, who works in a pharmaceutical company, was given an injection and some oral steroids at a clinic to control the allergy symptoms. Since the incident, she has stopped eating food that contains prawns.
Allergies can also come out of the blue and sometimes there are just no explanations for them, says Dr Adrian Chan, respiratory physician and intensivist at Mount Elizabeth Novena Hospital.
Citing his patient as an example, he says the woman was surprised when she developed rashes and breathlessness after consuming shellfish in her late 50s, as she had eaten it with no problems all along.
While adults may unexpectedly develop allergies, it is also possible for children to outgrow their allergies.
Children with milk, egg and soya allergies are most likely to outgrow them, says Dr Zeng.
About half of infants with milk allergy outgrow it by age five and half of children with an egg allergy outgrow it by six, he notes.
In contrast, peanut and shellfish allergies tend to be lifelong.
For peanut allergies, only about 20 to 25 per cent of children outgrow them, with four-fifths of these children doing so by eight years old. Seafood and tree nut allergies are believed to be lifelong and persist into adulthood, adds Dr Zeng.
There is no cure for allergies, but symptoms can be managed through treatment and by avoiding exposure to the allergen.
Dr Lau Pik Onn, senior resident physician at Icon Health Screening, advises those who are unaware of the cause of their allergies to keep a diary.
“Keep a record of what you come into contact with or have eaten on the day of, or days prior to, an allergic reaction. The fixed pattern of exposure can help you identify the potential allergen,” she says.
The Bottom Line: While it is not common, it is possible to develop an allergy to a substance or food in adulthood. There is no cure for allergies, but the symptoms can be managed through treatment and by limiting one’s exposure to the allergen.
- The Bottom Line is a series which aims to answer burning questions on health and well-being.
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