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Doctor Q&A

Friday Dr Q&A with Dr Liew – Allergy Tests

Dr Liew is a pediatrician who practices at the SBCC Baby & Child Clinic, Gleneagles Hospital Singapore and is also a visiting consultant to KK Hospital. He subspecialises in allergy, immunology and rheumatology. He was also awarded several research grants to pursue clinical research in paediatric anaphylaxis, drug allergy, primary immunodeficiencies and Kawasaki disease.

This was an original 4 week Friday Q&A, combined into a single more informative post.

Children’s Allergy Basics

Thank you Dr Liew for taking time to help answer these questions, we’ll start with the basic information on allergy.

What is an allergy? For children with eczema, should parents send their children to allergy tests or should only those with eczema of a certain severity do so?

Dr Liew: An allergy is simply an abnormal immune reaction to a common protein. Symptoms are varied depending on trigger and organ involvement. The most common reaction is on the skin, resulting in itchy rashes like urticaria (hives) or eczema flares.

Atopic eczema starts essentially as a skin barrier defect, with resultant dryness, itch and allergen sensitisation later. It is not a pure allergic disease. Skin tests for eczema patients are generally not necessary, as the most common allergen is house dust mites. Food triggers are more commonly in young infants with significant eczema despite good skin therapy.

Allergy vs Intolerance

MarcieMom: Allergy and intolerance are often mixed up; can you explain the difference between the two, specifically:

How a parent can correctly identify if the child is allergic or intolerant and what follow-up action they should take in each case?

Dr Liew: Allergy and intolerance result in adverse reactions, but the key difference is that the former involves the immune system, whilst the latter do not. If the immune system is involved, there is a potential for severe allergic reaction called anaphylaxis with continued exposure due to immune memory. There is no risk of anaphylaxis in intolerance. Eg. Cow’s milk allergy can result in hives, vomiting and wheezing; in contrast, cow’s milk intolerance presents with diarrhea in lactose deficient individuals.

Skin Prick Test for Kids

Common questions on allergy tests: There are a few allergy tests available – skin prick test, blood IgE test and patch test.

Can you explain a little more about these tests, how it is done on a child and how can a parent decide which to bring their child for?

Dr Liew: The type of allergy test recommended is based on the allergy symptom of the patient. As eczema is a mixed IgE/non-IgE driven disease process, tests for IgE like SPT and blood tests may be useful if positive, as targeted elimination may be attempted. If the tests are negative, empiric elimination of 2-3 weeks duration may still be considered if there appears to be a consistent food trigger.

Prolonged food avoidance however is not necessary and may result in malnutrition.

A skin prick test (SPT) is probably commonest and simplest allergy test performed in outpatient clinics. Essentially it is a scratch test with either a needle or plastic device, thus introducing a tiny amount of allergen protein under the skin surface. The test is completed within 15 minutes and measurement taken. A positive reaction appears as a small hive-like wheal and surrounding redness. It is good for identification of IgE mediated allergic reactions, and also for trending allergy sensitisation over time. Antihistamines would need to be ceased for 5-7 days, and there must be an area of clear skin (preferably the back in young children) for the test to be done. This is my preferred allergy test as there is minimal pain (especially with plastic devices), and results immediate. SPT also correlate better with allergic reactions if properly performed, as it takes into account the blocking antibody responses when the body is “outgrowing” an allergy.

Blood IgE Test

Allergen specific IgE test can also be easily performed for IgE mediated reactions. This is sometimes preferable if the patient has severe eczema and unable to tolerate cessation of antihistamines, or has minimal normal skin to perform the SPT. Blood tests are generally more expensive, as each allergen protein tested cost around $30. Results are usually known within a week.

Patch Testing

Patch tests are designed to test for delayed allergic reactions, rather than acute IgE reactions as the above 2 tests. Patch tests involved placing small area of allergen protein coated on wells or filter paper, and leaving them as a skin patch for 48 to 72 hours. A reading is then performed to look for delayed hypersensitivity reactions and the skin reaction graded. As there are several confounding factors for a successful test, patch tests are currently not recommended for clinical use but confined to research studies.

What to do after Your Child is Tested Positive for Allergens?

Given that allergy tests are not 100% accurate, parents may start to rely on an elimination diet strategy. 

Can you explain how much you would rely on each allergy test and whether they serve a different purpose in your diagnosis?

Dr Liew: Standard allergy tests are accurate, but have their limitations. Unvalidated tests for food allergy include blood IgG testing, intradermal skin testing, applied kinesiology, electrodermal testing, hair mineral testing, and iridology, and should not be performed. Eczema is a chronic medical condition with no curative treatment currently, and some patient would undertake extreme measures to look for the “elusive trigger”.

I would remind your readers that eczema is a skin disease, and not an allergic disease. Removing triggers can reduce the eczema, but will not cure it.

Food Elimination for Kids

Empiric food elimination may be considered for 2-3 weeks if a consistent food trigger is suspected. An objective assessment should be made if food elimination has resulted in any change. Food triggered eczema would improve significantly with elimination. If there is no improvement, as in the majority of cases, the food should be introduced and assessment made if there is a change. I would caution regarding multiple food elimination as I have seen really malnourished and stressed out patient and families.

Young Children’s Developing Allergy Profile

MarcieMom: I understand that it’s good to send the child for a re-test, to check if he or she has outgrown any allergy or developed new ones. 

What’s the reason for the change in the allergy profile of the child? Also, how often do you recommend a re-test and would your recommendation differ for a child who has different type of allergies and/or differ for a child who has different level of severity in eczema?

Dr Liew: Retesting is sometimes required in food allergies, but generally not necessary for eczema. The allergic profile of an individual changes according to his/her immunity and exposure to environmental proteins. We often see food allergens being “outgrown”, but a gain of house dust mite sensitisation with time. Retesting is usually considered if there is a new allergic disease eg. Allergic rhinitis, rather than based on fluctuation in eczema severity.

Common Pediatric Allergens

Based on your experience and knowledge of research studies, what are the common allergens in children? 

Dr Liew: The most common allergens depend on the allergic conditions. For eczema, older patients tend to be sensitised to house dust mites, but not food allergens. Some young infants with eczema has food sensitisation and trigger. The most common food allergens in eczema children include egg, cow’s milk, wheat, peanuts and soy. Some forms of food allergy eg, allergic enteropathy presents with isolated intestinal symptoms without skin involvement.

If a parent suspect a food is causing an allergy, should the parent insist on it being an item to be included in allergy test? 

As a pediatrician, would you test the child on what the parent suspect?

Dr Liew: A detailed history would be obtained prior to allergy testing. If there is a suspected food trigger, I would usually test it. I would usually encourage targeted testing, whereby only the relevant food items are tested. For eg, should the child be tolerating cow’s milk formula for the past 3 years, and eczema commenced after 3 years old, cow’s milk protein is unlikely to be a food trigger, and should not be tested.

Gluten and Eczema

MarcieMom: Gluten has been gaining more awareness and with many food packaging labeling gluten-free, some parents may think it’s gluten that’s causing the eczema. 

Again, how can a parent identify if it’s gluten (is it even a common trigger?) that’s triggering the eczema?

How can this be differentiated from celiac disease?

Dr Liew: There should be a close temporal relationship between food ingestion and eczema flare. If there is inconsistent relationship, it is unlikely a food allergy. Celiac disease is an immune-mediated reaction to glutens, resulting in malabsorption in the gut, and resultant bloatedness, diarrhea and weight loss.

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Doctor Q&A

Friday Dr Q&A with Prof Hugo – Skin Prick Test

Q&A Senior Consultant Allergy Immunology Professor Hugo for EczemaBlues

Professor Hugo van Bever is a Senior Consultant in Pediatric Allergy and Immunology at the National University Hospital, Singapore. He is an active member of the board Asia Pacific Academy of Pediatric Allergy, Respirology and Immunology. He is also my co-author for Living with Eczema: Mom Asks, Doc Answers!

This is originally a series of Friday Q&As in 2012 which has been combined into one informative post.

Eczema Baby Scratching Eyes

MarcieMom: Babies tend to scratch their eyes when tired. Also, I notice that my baby’s eyelids (where eyeliner is applied) look oily. To soothe the discomfort, I would wet a cotton pad with lukewarm boiled water and clean outwards. This is sometimes followed by moisturizing sparingly when her eyelid is dry.

How would you recommend a parent to reduce their child scratching eyes?

Prof Hugo: Keep eczema under control and apply a preventive approach.

Skin Prick Test for Kids

Marcie Mom: Today’s questions is on skin prick test, something I always recommend parents to do (in this post).
In a skin prick test, typically a few common food allergens such as egg and milk will be tested instead of all possible food that the child may eat. Why is testing a few of these food allergens sufficient to diagnose if there’s an underlying food allergy?

How often should a child get retested for food allergy? And what type of patients needs to be retested regularly?

Anti-histamines should be avoided before a skin prick test so as to avoid incorrect results (due to no reaction seen when there should be one). What else should a parent take note before bringing the child for allergy test?

Prof Hugo: Because only a few foods are involved in eczema, mainly in young children. These are: cow’s milk, egg, wheat and soy. Other foods are very seldom involved in eczema. In older children food allergy is usually not involved in eczema. Older children have mainly an allergy to house dust mites.

If the child improves there is no need to repeat skin prick test.

Skin prick test should be performed only when the child is in good health (no ongoing infection, no fever) and did not take antihistamines for at least 3 days. Antihistamines may suppress the skin prick test’s results, leading to false negative results. Skin prick test also needs an area of normal skin. In cases of severe eczema, skin prick test’s results are difficult to interpret. A blood test might be an alternative.

Topical Steroid as Treatment

MarcieMom: Many parents are worried about applying steroid cream for their child’s eczema. Recent research has shown that there is no major negative effect on the skin of children who have applied topical steroid over approximately 10 months, including no evidence of skin thinning.

What guidelines will you provide parents when applying steroids for their child (in terms of when to apply, how much to apply and which part of the skin to apply which steroid’s strength)?

Prof Hugo: Use mild steroids (for children) maximum 2 x day. Use them only on active inflammation (= “red” patches) and use them after cleaning the patches. Don’t use steroids on a dry skin or on old lesions.

Oral Steroid as Eczema Treatment

Marcie Mom: I must thank you again for helping Marcie with her eczema. I noticed that it got much better after the one-time oral steroid course you prescribed (read more in this post).

Oral steroid such as prednisolone is sometimes prescribed for children with severe eczema. Can a child only be prescribed oral steroid once? I’ve read horror stories online of how some doctors negligently keep prescribing oral steroid to the point that it no longer works for the child. How can a parent assess if the doctor is taking due care in his prescription for their child?

Prof Hugo: Oral steroids should be avoided, especially because eczema is a chronic disease, and oral steroids cannot be used chronically. Only in severe flare-ups a short course (5 to 7 days) is recommended. In some children (exceptionally) a longer treatment can be needed. However, this should be given in an EOD dose (= every other day). It is all a matter of trust in your doctor. If your child has severe eczema, needing oral steroids, I advise to see a paediatric allergist or paediatric dermatologist.

Alternative Eczema Treatments

Marcie Mom: Lots of parents are looking for a way to manage their child’s eczema (though a reminder that eczema is chronic, no miraculous cure) and may be willing to try ‘alternative treatments‘.

Many alternative treatments, including using natural remedies are marketed for eczema. Personally, I prefer sticking to moisturizing and appropriate use of steroid under doctor’s instruction. However, I understand the anxiety parents have when their child’s eczema hasn’t responded well to their doctor’s treatment.

What advice would you give a parent when deciding if they should try out a natural remedy? What is safe for them to try and what should they be wary of?

Prof HugoOnly use treatment that has been scientifically proven to be safe and effective. Many alternative treatments are available, without any study and without prove of effect: don’t try them out!

Partially Hydrolysed Milk

Marcie Mom: I have experienced switching to partially hydrolysed milk when Marcie was diagnosed with eczema.

Some research showed that giving babies partially hydrolyzed milk may reduce chance of milk allergy. I understand that it doesn’t alter the allergic profile of a child but may reduce chances of allergy as part of the milk protein is broken down. What is an allergic profile (is it part of DNA)?

Prof HugoHydrolysed milks can prevent cow’s milk allergy: that’s all. They have no effect on the long-term development of allergy. An allergic profile refers to the clinical presentation of allergy, and has nothing to do with DNA.

Food Restriction in Early Childhood

Marcie Mom: I also read that restricting a food in early childhood and introducing it later may lead to even more serious allergic reaction. What’s your understanding of how the same food allergy could progress from childhood to adulthood?

Professor Hugo: This is very individual and still confusing, because an intervention cannot be beneficial for all children, but should be tailored. More research on this is needed.

Vacuum Cleaner Selection

MarcieMom: Do you think the expensive vacuum cleaners are worth investing in? What should a parent look out for when buying a vacuum cleaner?

Prof Hugo: In case of house dust mite-allergy, a decent vacuum cleaner is recommended. However, most companies have no research data on their vacuum cleaner. Don’t spend too much money!

Sun & Haze Affect Kid’s Eczema?

MarcieMom: I read that the sun can dry the moisture on skin. Should children with eczema avoid the sun?

Prof Hugo: Active eczema (= skin inflammation) should avoid the sun.

Marcie Mom: I noticed that whenever there’s a haze (from neighbouring countries burning forests), my baby scratches a lot more. What could be in a haze and why does it irritate my baby’s skin?

Prof Hugo: Never been proven that the haze (= a type of pollution) has effect on eczema.

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Doctor Q&A

Questions I asked at webinar hosted by DrSearsLean

Dr Sears L.E.A.N. webinar on The Pros and Cons of Soy (image from DrSearsLean.com)

It’s another first for me, participating in a webinar, this time hosted by DrSearsLean. The webinar was conducted by Dominique Hodgin, MA, NE, the Executive Director of Education at DrSearsLean and Nutritionist. The presentation covered the definition of soy as well as the positive and negative effects of soy. I’ll leave to DrSearsLean to update you on the presentation which will be made available on his website; for me, I managed to get my questions related to eczema children answered and presenting to you as fast as I can!

Marcie Mom:   For infants who are diagnosed with eczema, should they switch to cow’s milk alternative like soy or goat or partially hydrolysed milk?

Dominique: A lot of the soy-based infant formula are isolated soy proteins which can potentially create some problems associated with soy isolates. If non-soy formula can be consumed by the infant, it’ll be better to consume a non-soy one. Dr Sears recommended in his book that even if the infant has to use a soy formula, it is good to try to reintroduce lactose at a later age.

Marcie Mom: Can a skin prick test accurately detect a soy allergy? How young can an infant take a skin prick test?

Dominique: Yes, a skin prick test can detect a soy allergy. Infant, as young as 6 month old can take a skin prick test (younger than that, may not be accurate).  Of course, to be sure, you can check for symptoms of allergy whether present/absent after eliminating soy from the diet.

Marcie Mom: For moms with cow’s milk allergy, would drinking soy during pregnancy instead of cow’s milk, reduce chance of baby developing soy allergy? (actually, I typed in the incorrect question, wanted to ask if it’d reduce chance of baby developing milk allergy)

Dominique: Not necessary. Milk allergy is a broad term, as there are various components that one may be allergic to, say whey. In any case, no definite on moms’ diet on baby’s development of allergy/not. Do also note that one does not only consume soy through drinking soy, as soy is present in many packaged food. Key is not to over consume soy.

Read more on food allergies for children, including soy allergy

Learn more from nutritionist and dietitian Judy Converse MPH LD RD about breast milk, cow’s milk and other alternatives

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Eczema Facts

Is your Eczema Child (Wrongly) Avoiding a Tested-Positive Food in SPT?

Skin Prick Test (SPT)

If your child has eczema and has been avoiding a food that he/she has been tested positive in the Skin Prick Test (SPT), it may be time to review if there is indeed a true food allergy. Research indicates, as I understand from various online articles, that the skin prick test is a test of sensitization, and not clinical relevance. Below are some points on the accuracy of skin prick test:

1.      Skin Prick Test is more accurate for non-food allergen, such as dust mite and pollen, than for food allergen.

2.      Skin Prick Test is More Accurate in predicting when there is NO food allergy and Less Accurate in predicting a Positive food allergy. The implication of this is that children who have been avoiding food (for example more than 50% of those tested positive for milk and eggs, and more than 70% of those tested positive for peanuts) actually didn’t have an allergic reaction to these foods. (There is only a 0.5-10% chance that a child who is allergic to a food will test negative for it.)

3.      Follow-up tests are required for skin prick test for children at different age, sometimes about 1-2 years later. The results can be different as children may ‘outgrow’ some allergy or develop new ones? (hopefully not…)

4.      An oral food challenge is the most accurate (less than 5% incorrect).

5.      For children with eczema, there is an 80% possibility that food that the child is avoiding turn out not to be one he/she is allergic to. Refer to this article for detailed research.

Despite above, Skin Prick Test still remains the most recommended first test for allergy, as it is by comparison simpler, lower cost, faster results, more tolerated (children won’t feel much pain, you can read this post on my baby Marcie’s experience) and more accurate than blood test. If anyone has an experience to share on skin prick test for your child, do comment below this post.

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Eczema Facts

Taking the fear out of the Skin Prick Test

Skin Prick Test (image from eatstudy.co.uk)

Sending a baby or a young child to a skin prick test may be fearful for you or your child.

My baby girl, Marcie, had her skin prick test about 7 months old when I gave up trying to identify what triggered her eczema flares (some days I thought it’s the stage 1 food she was having and some nights I drove myself paranoid researching all sorts of allergies). Prior to the skin prick test taken at Singapore’s National University Hospital, I had some fears of the skin prick test myself; I imagined that Marcie’s skin will be pricked all over with many holes to test for all possible food she will eat in her lifetime and I also imagined the needle to be like a syringe that will inject the possible allergens into her skin.

A Quick Prick that tells a lot

It turned out that the skin prick test is about 20 minutes, starting with the medical staff cleaning Marcie’s inner forearm and applying the possible allergens (egg, dust mite, cat’s hair, dog’s hair, milk, mold) onto her arm. While one staff proceeded to prick Marcie’s skin with a needle to allow the substance to enter her skin, another staff was playing with Marcie. Marcie did not cry or even whine but I think that’s because her usual itch is far more ‘painful’ than that little prick. We had to wait 20 minutes or so before the medical staff examined the size of the wheal, i.e. reddish swelling to determine if Marcie is allergic to any of the substance.

What the Skin Prick Test Results say

All the results tested negative and as mentioned, this takes a lot of stress out – no worries over food allergy (apparently, testing for milk and egg is sufficient for food allergy; no need to prick 100 holes to test for all possible food to be consumed in a lifetime).

Don’t try pricking at home

It was a blessing that Marcie did not show any allergic reaction. However, if there is a reaction to the allergen, there will be swelling that is bigger than the dummy test and also itching. The test is not to be done at home without medical staff in case of severe reactions to the allergen. The skin area to be tested must also be free from rashes, otherwise, the reactions will not be visible. Plus, consumption of anti-histamines should be avoided otherwise the skin may not show a reaction (when there should be one).

I strongly encourage parents to bring their child for the skin prick test, otherwise, you may drive yourself paranoid guessing what causes the eczema..