Are you having allergic reactions to foods or other substances? Do certain environmental conditions trigger skin rashes? It’s best to get tested. Here, we look at some common food intolerances, skin allergies and hay fever, plus the relevant tests for them.
Allergies can present in a variety of ways, according to Dr Benjamin Loh, a general practitioner at DTAP Clinic (Dr Tan and Partners). “Although the subject warrants more research, allergies tends to occur in patients with genetic predispositions. This is augmented by environmental factors such as allergens, eventually leading to a cascade of inflammatory processes in various parts of the body,” he says.
#1 Respiratory allergies
Respiratory allergens are inhalant particles, which can trigger airway reaction. Common examples include dust mites, mould, pollen and household pets, says Dr Loh. Though the severity of symptoms depends on the individual, respiratory allergens can affect a patient’s skin, eyes and airways.
One of the most common allergic respiratory conditions is allergic rhinitis (or hay fever) – thought to affect around 10 to 30 percent of the global population. Symptoms may include a stuffy or runny nose, sneezing, and itchy and watery eyes. It’s often associated with allergic conjunctivitis, an inflammation of the eye. Asthma is another type of respiratory condition in which there are airway spasms, causing coughing, wheezing and chest tightness.
Dr Loh says asthma can be controlled by avoiding allergens, and by using inhalers and certain medications. There’s also an option known as sublingual immunotherapy, which can help patients with conditions like allergic rhinitis and asthma. It is an alternative way to treat allergies without injections, where the patient is given small doses of an allergen under the tongue to boost tolerance to the substance and lessen symptoms.
#2 Food allergies
Food allergies occur when the immune system wrongly recognises proteins in a food as harmful, and, in turn, protects itself by releasing chemicals such as histamine, which causes inflammation.
“With a food allergy, the patient normally experiences adverse reactions caused by an increase in ‘sensitivity’ of the immune system. It usually happens almost immediately after ingesting the food or, rarely, a few hours after,” says Dr Loh.
Reactions can range from mild itching, rashes, hives and facial swelling to wheezing, congestion and gastrointestinal symptoms such abdominal pain, nausea, vomiting and diarrhoea. A more dangerous effect may include anaphylaxis, a life-threatening reaction. Patients with severe food allergies should have medications on standby for times of emergency.
According to Dr Loh, the two most common groups of food allergies are seafood (particularly shellfish) and nuts (including tree nuts and peanuts). Cow’s milk, eggs, soy and wheat are some of the other common food allergens, which are best treated with strict avoidance.
“Food allergies in children normally begin in the first two years of life,” he says. “There are certain allergies that a child might outgrow, including cow’s milk and eggs; other allergies like nuts or seafood are likely to persist into adulthood.”
It’s important to establish the exact food allergy a child has, as avoidance of that food may have an impact on the nutrients they’ll receive, says Dr Loh. He adds, “After confirming a food allergy, there is evidence to show that strict avoidance might increase the likelihood of outgrowing the childhood food allergy.”
#3 Other allergies
Apart from food and inhalant allergies, there are drug allergies, insect allergies (when the sting or venom creates an allergic response) and contact allergies to materials like nickel or cobalt.
“Many patients with atopic dermatitis have a genetic predisposition with filaggrin gene defects, leading to a weaker skin barrier. This makes them susceptible to external environmental factors including allergens. Removal of the allergens might improve a patient’s eczema,” says Dr Loh.
Which test is right for me?
It’s always best to seek a consultation. “Through a careful clinical history, your doctor will work with you to identify the possible allergens, the determination of exposure of allergens and the symptoms experienced. He or she will then discuss which tests are suitable or if there’s even a need for allergy testing.”
The skin prick test is considered a reliable method for identifying allergies. Usually performed on the upper back or inner forearm, it yields same-day results. The test site is cleaned with alcohol before small markings are drawn on the skin; a drop of allergen extract is applied to each marked area, and tiny lancets that barely penetrate the skin surface are used to introduce a very small amount of the allergens into the skin. Not to worry, there’s no blood or pain involved!
Once the test is complete (around 15 to 20 minutes), the patient’s skin is observed for specific reactions, which appear as red, raised and itchy bumps that look like mosquito bites. The bump’s size is then measured to confirm the allergic reaction, says Dr Loh.
While the skin prick test can be slightly more accurate than a blood test, Dr Loh says the tested allergens are limited mostly to more common ones – pet dander, mould, pollen and dust mites, for instance. More obscure allergies might need to be identified through a blood test.
The skin prick test is also not recommended for patients with severe allergic reactions, histories of anaphylaxis, certain skin conditions, or those using certain medications like antihistamines or antidepressants. Blood tests should also be considered in those cases, and for adults with existing heart or medical problems, says Dr Loh.
A comprehensive blood test can test for anything from guinea pig and honeybee venom reactions to strawberry, squid and hazelnut allergies. Results typically take around one week, after which the patient can discuss appropriate allergy management with their doctor.
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