Allergy alert wristbands

One of the concerns of parents of children with food allergy is that their children might be given something inappropriate to eat by someone unaware of their condition. Even for adults with food or drug allergies, in the event of an accident or a serious allergic reaction, emergency medical personnel might not be aware of their problem and inappropriate treatment might be given. The allergy alert bracelet enable patients to indicate their medical condition in a discreet manner.


The latest product on the market that has proven very popular with kids as well as adults is the Mediband. These come in a variety of colors and designs, and can be worn either with the alert prominently displayed or hidden on the inside. They are made of hypoallergenic material and the cost is low. We have ordered these bands in a variety of different sizes so there will be a good range of choices to choose from.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Update on peanut allergy

Food allergy is consistently one of the most anxiety-provoking illnesses for patients or their caregivers, especially if the problem is life-threatening. Eating is something we do several times a day, and the fear that danger lurks within every bite can seriously affect one’s mental well-being. Whereas desensitization treatment has been used for the treatment of allergic rhinitis and asthma for many decades, previous attempts to develop vaccines for food allergy have ended in failure. 

In the last two years, several studies of oral peanut desensitization have been published. While the majority of patients could be successfully desensitized, this treatment is limited by the high rate of adverse reactions and the need for close monitoring.

Sublingual desensitization is a new method of administering desensitization treatment for patients suffering from house dust mite and pollen allergies. Recent studies have shown effectiveness for patients suffering from allergic rhinitis and asthma. The advantages of this form of treatment include convenience and safety.

 A recent study of sublingual desensitization for peanut allergy shows encouraging results. The study was carried out at Duke University in North Carolina and Massachusetts General Hospital in Boston. Eighteen children were given sublingual drops of a peanut allergen extract or placebo at increasing doses. None of the patients suffered severe adverse reactions, with only oral itching as the most significant side effect.

After 12 months of treatment, those who took the extract could tolerate 20 times the amount of peanut given in an oral challenge than those who took placebo. The average amount tolerated was 1700mg, which was equivalent to 6 – 7 peanuts. Presumably, these patients could continue to eat peanuts regularly to maintain their desensitized state thereafter.

We have started to perform sublingual peanut desensitization using the same extract recently and several patients have been successfully desensitized. We are hopeful that this would become a viable alternative for the majority of patients suffering from peanut allergy.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Sweat sensitivity and skin allergy

Many patients suffering from atopic dermatitis complain of itching and worsening of their rash after sweating. Many patients with atopic dermatitis have been found to have an allergic sensitivity to an as yet unidentified antigen in their own sweat. The majority of these patients develop positive skin test reactions to a 1,000 to 10,000-fold diluted preparation of their own sweat, whereas only 1% of the normal population has a similar reaction.

Another condition known as cholinergic urticaria has now been confirmed to be due to sweat allergy. These patients develop extremely itchy small hives on their skin when they are hot or when they exercise. The majority of these patients also have positive sweat skin test.

More interestingly, recent clinical studies in Japan suggest that sweat desensitization treatment might be effective for these conditions. Six Japanese patients with cholinergic urticaria underwent desensitization by intradermal injections of escalating doses of their own sweat. Five out of six patients showed significant symptomatic improvement. We have started to offer sweat skin test to our patients who have symptoms of sweat allergy. In those patients with positive reactions, sweat desensitization might be a viable treatment option. This might be particularly valuable to those patients suffering from cholinergic urticaria, as there is currently no other viable treatment option for these patients except antihistamines.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Eczema and dermatitis (2)

 

Treatment of atopic dermatitis should first and foremost include repairing the skin barrier function to reduce allergen penetration. This can be accomplished by the regular use of barrier ointments. Food allergy is often an important factor in patients under the age of three, but diagnosing allergy in atopic dermatitis is full of pitfalls. These patients generally have very high total IgE antibody levels, rendering the use of allergy blood tests unreliable; in the presence of a large amount of IgE, non-specific IgE binding occurs and a large number of false positive reactions are seen. Many patients erroneously go on diets avoiding many foods based on these findings, whereas most patients are only allergic to less than three kinds of food. Skin prick tests are more reliable, but only if done during disease remission. Skin tests performed on inflamed skin will also result in a large number of false positive reactions. We therefore always treat the dermatitis first and do allergy tests once the disease is under control. Topical steroid is still the mainstay of treatment, but must be monitored carefully as overuse can further damage the skin barrier and might also lead to rebound inflammation. In patients whose skin is colonized with bacteria such as Staphylococcus, regular use of bleach baths can greatly reduce the frequency of exacerbations. Patients who require excessive amounts of topical steroid might benefit from a course of oral immunosuppressive drug therapy.

Contact dermatitis can affect people without the above mentioned skin barrier defects, but patients with atopic dermatitis often suffer from contact dermatitis as well. Contact dermatitis often occurs after prolonged or repeated skin contact with certain allergens. Plant resins known as urushiols, for example, can cause dermatitis in up to 70% of the population, given enough exposure. These resins are found on the leaves of plants such as poison oak, poison ivy or poison sumac. They are also used as varnish on furniture and lacquer ware. Some people are so sensitive that even contact with molecular amounts of the urushiol allergens can lead to severe outbreak. The most common contact allergen seen in clinical practice is nickel, which is found in a wide variety of household objects such as coins, fasteners, utensils and jewellery, and also in food. Dyes, preservatives, anti-microbials and fragrances found in skin care products are also common culprits. Rubber glove and detergent are common causes of hand dermatitis.

Avoidance is the most important treatment for contact dermatitis. The cause of the dermatitis must therefore be accurately diagnosed so that the patient knows what to avoid. This is usually accomplished by careful history taking, identifying the possible allergens the patient comes in contact with. The diagnosis should be confirmed with patch testing, as contact dermatitis is caused by a cell-mediated rather than IgE-mediated immune mechanism. Avoiding the relevant allergens is usually all that is needed to successfully manage contact dermatitis.

 

 

 

 

 

 

 

 

 

eference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Eczema and dermatitis(1)

 

Eczema and dermatitis are terms that mean skin inflammation. The two most common types of dermatitis are atopic dermatitis and contact dermatitis. Whereas the two types of dermatitis are indistinguishable pathologically, there are differences in terms of epidemiology, etiology and treatment.

Atopic dermatitis usually starts in infancy or early childhood. The basic problem with atopic dermatitis is an inborn defect in skin barrier function. The skin is an important barrier that protects us from our environment, and normally does not allow allergens to penetrate through. Genetic defects that lead to a reduction in the barrier function allow substances to penetrate the skin more easily. The defects also increase water loss from the skin, and dry skin is a characteristic of this condition. Allergens that penetrate through the skin barrier interact with Langerhan cells within the skin, which direct the immune system to develop allergic sensitivity to these substances. Infants with eczema are therefore much more likely to develop food allergy, respiratory allergy and asthma. Eczema therefore predisposes an individual to developing allergies and not the other way around as previously thought. Once the patient develops allergic sensitivity to an allergen, exposure to that allergen through direct contact or ingestion then leads to allergic inflammation in the skin. Inflamed skin is dry, intensely itchy, rough and can become infected easily. Common allergens that can cause atopic dermatitis include food, house dust mites, chemical substances found in skin care products, rubber chemicals, metals, and even sweat and bacteria that live on the skin.

 

 

 

 

reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Challenge Testing ( Drug challenge & Inhalation challenge)

Drug challenge

Skin testing can only be used to diagnose allergy to a few drugs such as penicillin and insulin. Drug challenge, where increasing amounts of a drug is given orally, subcutaneously or intravenously, is sometimes used to confirm or exclude drug allergy.

Allergy to food additives, which are chemicals and therefore behave more like drug allergy, also requires oral challenge for diagnosis.

Inhalation challenge

The defining characteristic of asthma is reversible lower airway obstruction. As asthma symptoms are often intermittent unless triggered by external factors, diagnosis can be difficult.

Drugs such as methacholine or histamine can trigger airway narrowing in asthmatics, and are used in inhalation challenge to diagnose asthma. Other specific asthma triggers such as aspirin and allergen can also be used.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Challenge Testing (Oral Challenge)

Challenge testing is the gold standard for diagnosing allergy. Challenge tests commonly performed by allergists include food challenge, drug challenge, inhalation challenge and physical challenge (heat, cold, exercise).

Oral Challenge

Skin prick tests and specific IgE blood tests are often used to aid in the diagnosis of food allergies. However, having positive skin tests or specific IgE to foods does not necessarily mean that the patient is allergic to those foods. The reason is because the body can develop an immune response called oral tolerance that suppresses the food allergy while the skin or blood test remains positive. Therefore, young children with food allergies often develop tolerance when they grow older while their test results remain positive for a few more years. On the other hand, negative skin or blood tests can reliably exclude immediate-type food allergy.

Allergists therefore use food challenge to determine whether a patient is allergic to a particular food when there is suspicion that skin or blood test results are incorrect, or when the patient might have outgrown his/her food allergy. An open challenge is performed by simply giving the patient increasing amounts of the food under close medical supervision. However, a significant amount of psychological overlay is sometimes present, which will bias the result of the challenge. Therefore the food is often hidden in a vehicle such as apple sauce and given to the patient in a single-blinded (subject is blinded to the test condition) or double-blinded (both observer and subject blinded) manner, alternating with plain vehicle.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Allergy blood tests(4)

Appropriate use of allergy blood tests

Specific IgE blood tests are useful when skin testing is impractical, such as when patients have active urticaria (hives) or other skin conditions, or if patients cannot stop antihistamine treatment. Only tests that have been validated, i.e. tests that have received FDA approval or clearance, should be used. Blood test results must be interpreted with care, and positive results should be verified by challenge testing unless there is strong clinical evidence to support the results. The level of specific IgE might be useful in monitoring the progression of food allergies, since a declining trend of food-specific IgE is a good prognostic factor for eventually outgrowing that allergy.

The most commonly used FDA-approved allergy blood tests include RAST, MAST, CAP, UniCAP and chemiluminescence assay.

Can blood tests be used to test for "food intolerance" ?

Many laboratories performing non-validated blood tests claim that these tests can be used to identify food intolerance. Such tests typically test for dozens or even hundreds of foods using crude methods such as ELISA. Food intolerance is not a diagnosis, rather an umbrella term for any condition that produces symptoms due to food ingestion. Food allergy, for example, is a form of food intolerance. Other examples include enzyme deficiencies that can lead to indigestion or malabsorption of certain nutrients, pharmacological effects of food chemicals such as caffeine etc.

Since none of these conditions, with the exception of food allergy, involve food-specific antibodies, antibody blood tests have no role in making diagnosis. Any laboratory that claims that a blood test can be used to diagnose food intolerance is committing healthcare fraud.

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Allergy blood tests(3)

Blood tests for antibodies other than IgE

Studies in the 1970s found that IgG antibodies can also cause allergic reactions in rodents. Therefore, tests for IgG antibodies that bind to food were developed, because IgG antibodies are very abundant (several million-fold more concentrated than IgE) and hence very easy to measure with crude assays such as ELISA. However, IgG antibodies do NOT lead to allergic reactions in human beings. In fact, one of the mechanisms that the body uses to produce immune tolerance is allergen-specific IgG4 antibodies. IgG4 antibodies are immunologically inert, yet they compete with IgE for allergen binding, and since they exist at much higher concentrations, they can effectively block IgE-mediated allergic reactions. Accurate tests that measure allergen-specific IgG4 are useful in determining immunological tolerance, especially during desensitization therapy.

Despite their lack of effectiveness, IgG blood tests are still being heavily promoted for the diagnosis of food allergy and “intolerance”. Many patients have been misled by these tests into believing that they have multiple food allergies, and undergo unnecessary and even harmful food avoidance. More ominously, real food allergy remains undiagnosed, leading to fatal or near-fatal accidents. Any laboratory that promotes food IgG tests for diagnosing allergy is perpetrating healthcare fraud.

 

 

 

 

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Allergy blood tests(2)

Blood tests for specific IgE antibodies

As mentioned in previous articles, allergic reactions can be mediated by different immune mechanisms. The most common type of allergic reaction is mediated by IgE antibodies, and therefore most blood tests for allergy seek to measure allergen-specific IgE. Most of these tests will also measure the total IgE level. There are several obstacles that developers of blood tests must overcome. First, IgE antibodies are mainly found on the surface of mast cells, and the amount of free IgE in the blood is miniscule, and might not truly reflect what is found on the mast cells. Therefore, extremely sensitive methods must be employed to measure these antibodies. These tests employ allergens that are bound to a solid phase to capture IgE antibodies in the blood sample. Anti-IgE antibodies are then used to detect these captured IgE antibodies, and the signal is amplified using enzymatic reactions or radioactivity. This amplification process increases the background noise of the assay, and greatly increases the chance of false positive results.

Second, these assays only measure the binding of IgE to the allergens on the solid phase. While IgE binding is the essential first step during an allergic reaction, it does not necessarily lead to the complete allergic reaction, just as a key that can be inserted into a lock does not guarantee that it can open that lock. Therefore, antibodies that are structurally similar to the antibodies that are being measured will also show up in the assay, but these cross-reacting antibodies might actually be specific for bacterial or other irrelevant antigens. This problem is extremely common in patients with very high total IgE levels, such as patients with eczema who has repeated skin infections. On average, there is a greater than 50% chance of a positive food IgE test result being false. Therefore, the guidelines published recently by the National Institutes of Health in the United States advised against using blood tests to diagnose food allergy.

 

 

 

 

 

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.

Allergy blood tests(1)

Diagnosing allergy is a subject that is very commonly misunderstood. One of the commonest misunderstandings concerns the role of blood tests in managing allergies. When considering the use of medical tests, there are several pertinent questions that need to be answered.

l   How sensitive is the test ? In other words, what percentage of patients with the disease will the test identify ?

l   How specific is the test ? That means, what percentage of patients without the disease will the test exclude ?

l   What is the positive predictive value ? That means, what percentage of patients with a positive test result really has the disease ?

l   What is the negative predictive value ? That means, what percentage of patients with negative test result really does not have the disease ?

And of course, the most important question: How does the test result affect the management of the patient ?

 

 

Reference information: www.allergy.hk/

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.