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 Allergy

Allergy Symptoms and its Treatment at Medical Express Clinic

Allergy is a widespread disease, which is becoming increasingly common worldwide and has a tendency to aggravate with time. Currently, more than 20% percent of the population suffer from respiratory allergies. A similar numberof people may have food allergies. About 15% of babies under 1 year have food allergies.

Impact

For most allergy sufferers, their allergy leads to a significantly reduced quality of life, affecting studies, work and leisure time. Meal preparation and going to restaurants are problematic. For children, playing at a friend's house, birthdays, sleepovers and more are affected. Parents of children with allergies have increased stress. Allergic patients can relieve symptoms by self-imposing restrictions on activities to avoid allergen exposure. Self-imposed restrictions may have psychological and social consequences.

Allergic disease has significant socio-economic impact on the patient, the patient's family and the society as a whole. According to a European survey of diagnosed allergy sufferers, around eighty percent of the respondents find that their disease considerably affects their daily activities. Many allergy sufferers are recommended to carry treatment and adrenlilne injections (such as EpiPen). The growing prevalence of allergy has major economic
consequences for society through reduced working
capacity and more sick leave, placing a greater burden on
healthcare resources and increasing medication costs.

 

How can you find out if you suffer from a food allergy?

Signs and Symptoms

The clinical manifestations of IgE-mediated allergy to foods are extremely diverse. They may involve the skin (urticaria), the respiratory system (asthma) and the oral mucosa (swelling, redness) as well as the gastro-intestinal tract (nausea, vomiting, pain and discomfort). Atopic dermatitis is also associated with food allergy. Brain allergy is also common; presenting with depression, irritability, sleep disorders, ADHD, etc.
 
Reactions can occur minutes to hours after exposure to the allergen. The most severe of these reactions is anaphylactic shock, which combines several of those symptoms. Typical signs can include peripheral vasodilatation leading to circulatory collapse, accompanied by swelling of the skin and mucosal tissues (angioedema), which results in breathing difficulties. Untreated anaphylactic shock can rapidly result in death. A second severe, and potentially fatal, manifestation is Quincke's oedema, the typical signs are swelling of the deep layers of the skin and mucous membranes, such as those of the throat. Technically, it has been described as localised anaphylaxis.

Diagnosis

Diagnosis of food allergy requires a combination of clinical history, laboratory (specific IgE measurements) or outpatient (skin prick tests) tests and challenges with the food. Food challenges are risky and should be carried out in a hospital evironment.
 
Diagnosis of an allergy involves a clinical doctor drawing together three different kinds of information:
 
A detailed history of past allergic reactions and other allergic conditions, such as asthma, eczema and hayfever, and consideration of any seasonal or environmental symptoms.
 
A thorough medical examination, involving peak flow measurements if the patient is asthmatic, and a close look to see if there are allergic symptoms in the skin, eyes and nose. This information will help the specialist decide which tests are appropriate.
 
Results of allergy tests; usually skin prick testing or blood testing.

What do these tests involve?
 
Is skin prick testing dangerous?
 
At what age can testing be given?
 
Are the tests that are offered reliable?
Here, we attempt to answer these and other common questions.

A book called "Not All In The Mind" written by Dr Mackarness, a consultant psychiatrist is worth a read.


 
 

Secondary Effects of
Allergic Disease

  • Decreased quality of life
  • Sleeping disorders
  • Learning and attention impairment
  • Mouth breathing dental malocclusion

Mental Effects of
Allergic Disease

  • Feels tired
  • Feels miserable
  • Feels irritable
  • Depression
  • Embarrassment

Treatment

After food allergy has been diagnosed, the only treatment measure that can be offered is to avoid the offending food. This makes it very important to provide consumers with clear information about the composition of foods.
 
Food avoidance can also have serious nutritional consequences when it removes an important food group from a person's diet. For these reasons someone with a food allergy should consult a trained dietician before implementing a restricted diet.

If you think you have an allergy you need to consult a clinical doctor, to ensure that you receive a proper diagnosis.
 
Anyone who suspects they are at risk of sufferring an anaphylactic reaction should be referred to an allergy clinic.
 

Skin Prick Test at Medical Express Clinic

A skin prick test with standardized allergens is recommended by the EAACI (European Academy of Allergology and Clinical Immunology) due to the high safety, the high diagnostic sensitivity, and its easy technical performance.
 
At Medical Express Clinic the skin testing is carried out by specialist nurses and or doctors if it is carried out as a part of a specialist allergy consultation. The test is carried out to EAACI guidelines and to a very high standard.
 
Skin prick testing or SPT demonstrates an allergic response to a specific allergen. In conjunction with an allergy focused history, SPT can help to confirm the presence of an allergy to either a food or inhaled substance (allergen). At Medical Express Clinic the allergy history is taken by the allergy questionnaire. You can download this and other relevant forms in the following column.
 
SPT is the most common allergy test performed for the diagnosis of allergy. SPT is a simple, safe and quick test, providing results within 15-20 minutes. This will enable you to receive a diagnosis and discuss management plan at your appointment.
 
SPT is not a test for food or inhalant intolerance. It is not a test for H.pylori infection.
 
The skin prick test introduces a tiny amount of allergen into the skin, eliciting a small, localised allergic response, in the form of a wheal (bump) and flare (redness) at the site of testing. These tests can be carried out on all age groups, including babies.
 
A skin prick test measures the reactivity of the mast cells/ mast cell bound IgE inside the human. The principle is to "provoke" a reaction in a person by adding a minor amount of allergen.
 

Method

A small drop of allergen extract is placed on the arm and with a lancet the skin is pierced and a very small amount of allergen is penetrated into the skin. If the patient is allergic, the patient will react with a weal and flare reaction. We have commercially made allergens (antigens) but SPT can also be performed using raw or cooked food. This is Prick-to-Prick SPT (Skin Prick Testing)
 
A positive and a negative control are always performed at the same time. The positive control is an SPT without allergen but with histamine. The histamine makes the same physiological reaction as the histamine from the allergic reaction and functions as a control. At Medical Express Clinic we have a positive control and negative control.  

Skin Prick Testing

Skin Prick Testing
 

Hypersensitivity (to food, inhalants) can be either Allergy or Intolerance. Allergy can be IgE mediated or Non-IgE mediated. Skin Prick Test (SPT) is a test for IgE mediated allergy. SPT is not a test for intolerance or Non IgE mediated allergy. People with hypersensitivity who have negative SPT will need to see a consultant specialist to establish if the symptoms they have are allergy related.
 

Please download and complete the following three forms before your appointment.

 

Skin Prick Testing is suitable for any age group. Even babies under a year old are tested at some clinics in this way. A tiny prick is made with a lancet through a drop of allergen placed on the skin, usually on the forearm.
 
A positive reaction will be indicated by itching within a few minutes. The site where the allergen was introduced then becomes red and swollen, with a raised weal in the centre that looks like a nettle sting. The weal enlarges and reaches its maximum size within 15-20 minutes, when the measurements of the weal are recorded. The reaction fades within an hour.
 
This method introduces such a small amount of allergen into the skin that testing is usually safe, even in cases of severe nut allergy. Dr. Bill Frankland, atop allergist, knows of only three cases reported in the world medical literature where skin prick testing caused anaphylaxis. This is out of millions of tests performed. We have noticed an increase in anaphylaxis in cildren under 4 years; and a slight increase in the age groups 5 to 14 and 15 to 34.
 
A negative response usually means the patient is not sensitive to that allergen. But skin prick testing for food allergens may be unreliable and "false negatives" can occur where the reaction to food is not immediate. A negative response may occur if the patient is taking antihistamines. Antihistamines should be stopped five days before SPT testing. Another cause is the fact that some allergens are very unstable; thus for many fruits and vegetables a doctor might use a "prick-prick" test, where a lancet is used to pierce the fruit or vegetable and then used to make the skin prick. At Medical Express Clinic we can perform prick-to-prick test; the patient must bring the antigen and ask the nurse to do the test.
 
A positive response usually means the patient is allergic to that allergen. However, a patient may have a positive skin test but suffer no symptoms when coming into contact with the allergen. Positive skin tests may also occur before an individual has experienced allergic symptoms to a food. People may also still have positive skin tests to foods and inhalants, even when they have grown out of the allergy and no longer have an allergic reaction on eating a problem food.
 
A skin prick test measures the reactivity of the mast cells/ mast cell bound IgE inside the human. The principle is to "provoke" a reaction in a person by adding a minor amount of allergen.
 
A small drop of allergen extract is placed on the arm and with a lancet the skin is pierced and a very small amount of allergen is penetrated into the skin. If the patient is allergic, the patient will react with a weal and flare reaction.
 
A positive and a negative control are always performed at the same time. The positive control is an SPT without allergen but with histamine. The histamine makes the same physiological reaction as the histamine from the allergic reaction and functions as a control.
 

 

Science commentary: Skin prick testing

From the Science Editor of The British Medical Journal
 

Skin prick testing is conventionally used to investigate immediate type hypersensitivity to allergens in patients with rhinoconjunctivitis, contact urticaria, asthma, atopic eczema, and suspected food allergy.
 
It is also a means of detecting allergen specific IgE and has the advantage of being relatively inexpensive, providing immediate results compared with measurement of serum allergen specific IgE by radioallergosorbent testing (RAST).
 
The technique used for skin prick testing involves puncturing the skin with a calibrated lancet (1 mm) held vertically, or a hypodermic needle or blood lancet at an angle of 45°, and introducing a drop of diluted allergen. All patients undergoing skin prick testing should also have a positive histamine control and negative diluent (saline) control test included. An itchy weal should develop at the histamine puncture site within 10 minutes. Test solutions are standardised to give a mean weal diameter of 6 mm. The maximum or mean diameter of the weals to various allergens should be read at 15 minutes. A weal of 3 mm or more in diameter is generally considered to represent a positive response (indicating sensitisation to the allergen). The negative control is important because it excludes the presence of dermographism, which if present makes the tests difficult to interpret.
 
The relevance of skin prick testing should be interpreted in the context of the patient's history. Positive results can occur in people without symptoms and, similarly, false negative results may occur. "Blanket" allergy testing (whether by skin prick testing or serological methods) can give false positive results and, particularly in the case of foods can lead to unnecessary dietary restrictions. Standardised solutions to a wide range of allergens are available commercially. For more labile allergens (such as those found in fruit and vegetables) fresh produce should be used. Skin prick tests to aeroallergens are generally considered safe, but intramuscular adrenaline should be available and full resuscitation facilities are needed when test are carried out with other allergens such as foods and natural rubber latex.

 
Abi Berger,
Science editor, BMJ

Note: SPT is a test for allery; it is not a test for intolerance. If a patient suspects intolerance the starting point is a consultation with a specialist Allergologist. At Medcial Express Clinic Dr Scott Peseirs will see such patients. Ring 0207 499 1991 for an appointment.

Currently, more than 20% of the population suffer from respiratory allergies.

Blood Tests

RAST (Radioallergosorbent test) and CAP-RAST are the most commonly used blood tests in the UK (the CAP-RAST seems to be superseding the RAST test because it appears to be more reliable and more sensitive). Other immunological blood tests not using radioactive material but enzymes are now superseding the original RAST methodology. They work by detecting the presence of a molecule, called IgE, which is involved in allergic reactions, which can bind a particular allergen. At Medical Express Clinic we can organise the blood test.
 
Blood tests give graded results from 1-6, with 6 being the most positive. Blood tests are not affected by antihistamines, and can be used in patients with severe eczema. A blood sample is taken and sent of to a specialised laboratory for analysis; as a result they are quite costly and the results are not available immediately. These tests also only indicate an allergy if the IgE is present in the blood, and there is not a clear relationship between the presence of IgE and the severity of the allergy. In some cases the blood test is negative, but an individual still experiences symptoms on consuming a food. This is explained by a Non-IgE mediated allergy (see table to the left).

 

Challenge Testing

At Medical Express Clinic we do not carry out Challenge Testing. A challenge test is more accurate than blood tests or SPTs. A patient who has had a genuinely life-threatening allergic reaction, like anaphylaxis, should probably not be challenged with the food that caused it. Past symptoms must be discussed thoroughly with the medical team offering the challenge.
 
Challenge testing MUST always be given under strict medical supervision, and by a specialist with a high degree of knowledge about allergy. At Medical Express we do not carry out any challenge test. It involves giving a patient increasing doses of the suspected allergenic food, allowing ample time between doses for a response to occur. Challenges are often conducted in a double-blind manner. This is when neither the patient, nor the investigator knowing whether the food being given has any allergen hidden in it or not. A safe challenge involves the following course of action by the medical team performing the challenge:

 

They must ensure the patient or person is fit and well before challenge. In particular, there must be an absence of asthma or wheezing. Antihistamines must be avoided during the week leading up to the challenge.
 
Careful planning of the doses to be used and anticipating the medical responses to reactions before starting. Ensuring resuscitation equipment is standing by.
 
Ensuring the patient and, if a child, the parent understand what is going to happen. They will have to sign a medical consent form.
 
Increasing the dose very gradually. For example, in a peanut challenge, the doctor or nurse might choose to start with a small piece of peanut (or peanut butter) rubbed on the lip. If there is no reaction after 10-15 minutes, they can proceed cautiously to the next stage.
 
The next stage might be allowing the patient to eat, for example, a tiny smear of peanut butter spread thinly on a small piece of bread. Gradually increasing the dose until, for example, 8-16 nuts have been eaten.
 
Many challenges are stopped too early due to anxiety, but it is necessary to proceed if the true picture is to be obtained.
 
A negative challenge is valid only if no symptoms are observed following exposure to a large dose of the problem food.
 
Adequate observation for up to four hours after the challenge.
 
A nurse or doctor assessing any allergic reaction.
 
Medication may - or may not - be necessary.
List compiled with the help of
Dr Jonathan Hourihane.
 

Conclusions

A detailed history and examination alongside the chosen test is required in order to give a complete picture, and make a correct diagnosis. As a consequence of the unreliability of many blood tests in predicting allergic reactions, skin prick testing remains the primary tool to confirm an allergic diagnosis, and gives the most reliable results. However, none of these tests are infallible. This is because the sensitivity and predictive ability of skin prick tests and specific IgE measurements varies considerably from food to food. It is very high for fish, for instance, but very poor in the case of apple allergy. Food challenges remain the "gold standard" for diagnosis, except where the patient has suffered an anaphylactic shock.

 
A skin prick test with standardized allergens is recommended by the EAACI (European Academy of Allergology and Clinical Immunology) due to the high safety, the high diagnostic sensitivity, and its easy technical performance.

Allergy is a widespread disease, which is becoming increasingly common worldwide and has a tendency to aggravate with time.


 



 
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