Chemotechnique Diagnostics AB
Diagnostic Patch Test products from the world leading manufacturer,
and supplied exclusively in the Caribbean Region
by AllerDerm Caribbean Ltd
Below are sections of interest for the Allergic Patient
on Allergic Contact Dermatitis and on Patch Testing.
THE CARIBBEAN PATCH TEST SPECIALISTS
Around the world, Allergic Contact Dermatitis may be diagnosed by a Primary Care / Family Practitioner, though more usually such a generalist doctor will have recommended their patient suffering from such a condition to be referred to a Specialist in Dermatology or perhaps Allergy. The reason is simply that there are various skin conditions that appear the same as Allergic Contact Dermatitis, and if the symptomatic therapy prescribed by the generalist doctor fails to adequately resolve the patient's discomfort, then a more precise diagnosis may be required, including identification of the cause and the source of the problem, so that avoidance measures can be implemented.
In many clinical cases, the apparent Allergic Contact Dermatitis may not be the only medical issue of the patient; for example the patient could also be allergic to various inhalant allergens such as House Dust Mite or pollen spores. In such cases the patient may already be under the care of a Specialist Allergist, who may then try to also diagnose and treat an apparent Allergic Contact Dermatitis.
In many clinical cases, the patient is under the age of 18 so may already be under the care of a Specialist Paediatrician. A Paediatrician would usually however refer the patient on to a colleague Dermatologist to investigate the apparent Allergic Contact Dermatitis.
Certainly, in the Caribbean region, cases of Allergic Contact Dermatitis would eventually be attended by a Dermatologist or an Allergy Specialist, or perhaps an Internist.
But even amongst Dermatologists, by no means all Dermatologists are involved with the diagnosis and treatment of ACD. Some Dermatologists focus on Skin Cancers; some Dermatologists focus on Aesthetic Medicine, and perhaps only one Dermatologist in three will focus on the classical practice of Dermatology that includes Patch Testing to identify problem substances that cause Allergic Contact Dermatitis.
So if you as a Patient, believe you may be suffering from an Allergic Contact Dermatitis due to a substance found in your workplace (an occupational hapten) or to some item in your personal life, then do not suffer unnecessarily...
- Ask your Retail Pharmacist for advice and for over-the-counter treatments to ameliorate your symptoms...
- Ask your Primary Care Practitioner for more potent treatments to ameliorate your symptoms...
- Ask your Primary Care Practitioner for a referral to a Specialist Dermatologist who offers a Patch Testing Service, whether in a State Hospital or in a Private Practice.
Contact allergy is the state of being sensitised to a hapten with which the person has come into contact with, usually by the skin.
What is a hapten, you may ask!
Good question!!
Essentially, a hapten is a substance, usually a chemical, that becomes presented to the immune system of a person, usually through physical contact between that substance and that person. Then the hapten becomes conjugated (attached) to an immune cell in a persons body, and this complex of hapten + immune cell then becomes an allergen. This allergen may then cause the development of symptoms of Allergic Contact Dermatitis. In many contexts, the substance is commonly known as an allergen, though it is technically and more correctly called a hapten.
Haptens are typically small, chemically reactive molecules with low molecular weight. They need to penetrate the horny layer of the skin (stratum corneum) in order to conjugate to (bind to) epidermal and dermal proteins forming “hapten-carrier complexes” with antigenic properties that are capable of causing contact allergy. Examples of widely recognised haptens include nickel, formaldehyde and preservatives in cosmetics.
You may also ask what is an antigen...
An antigen is (simply put) any substance with which the human body may develop an adverse reaction of one form or another.
Sensitisation to a hapten occurs when the accumulated exposure to that specific hapten surpasses a certain threshold. This threshold is individual and varies greatly between different persons. Some persons will develop an allergy the first time upon encountering a hapten, other persons can withstand a life-time of exposure to that hapten without becoming sensitised.
Allergic Contact Dermatitis (ACD) is a disease of the skin that emerges in people that are exposed to specific haptens after having developed contact allergy. Once allergic, the subject will respond with skin inflammation (redness, flaking skin or blisters) whenever exposed. Individuals handling haptens as part of their profession or work occupation run a higher risk of developing ACD.
Once that person has reacted (for example by the development of symptoms of Allergic Contact Dermatitis; ACD), then they are said to be sensitised to that hapten.
Once sensitised, if the person encounters that same (or a closely related) hapten again, then they will most probably react again with symptoms of ACD. Those reactions can be weaker or stronger than the first time around.
ACD accounts for 20% of all reported work-related skin diseases. Occupational fields with high occurrences of ACD include (but are not limited to) hairdressing, construction work, cleaning and health care.
Chronic once developed, and with no known cure, contact allergy is of major distress for those affected.
Do not confuse Allergic Contact Dermatitis which is a "Type IV" Delayed allergic reaction to a hapten with the classical "Type I" Immediate allergic reaction caused by usually biological substances ("allergens") such as pollens, mould spores, animal danders, house dust mite, foods, etc. Those usually cause respiratory reactions or gastro-intestinal reactions.
These allergens are identified usually by Skin Prick Tests
(not Skin Patch Tests) or by blood tests to identify allergen-specific Immunoglobulin E (IgE).
Still confused?
More confused?
Unfortunately many Family Practitioners/Primary Care Practitioners are too.
That is why the involvement of a Specialist Dermatologist or Specialist Allergist is advised whenever possible.
For further information, please see the list of recommended reading at the end of this section on Patient Information.
In order to perform a diagnostic Patch Test, two crucial components are required (besides the patient):
The Patch Test procedure is an epicutaneous diagnostic provocation test using standardised patch test Haptens and patch test Chambers on Chamber Strips.
The haptens may be a single chemical, (such as formaldehyde) or may be a mix of related chemicals (such as thiuram mix).
This mix counts as a single patch test.
Patch testing is performed by applying haptens into small chambers mounted on tape. These are known as Patch Test Chambers on Patch Test Chamber Strips or Patch Test Units. Once the different Haptens have been applied to the Chambers, then the Chamber Strips are applied to the patient’s skin, most usually on their back, for a period of 48 hours, or 72 hours.
In a person who is sensitised to one or more of the haptens in the Chamber Strips, the patient's immune system will react by producing a characteristic reddening, itchiness or superficial lesion at the site of the problem Hapten. This is a positive patch test reaction. There are grades of positivity. See the pic below.
The Hapten preparations used in patch testing should ideally be specifically developed for patch testing purposes.
The Patch Test Haptens manufactured by Chemotechnique of Sweden are prepared by mixing high-purity fine-particle ground raw material with high-grade white petrolatum. A few haptens are in liquid form, either ethanol or water.
The Patch Test haptens are grouped into Series. The typical patch test screening is performed by testing a Baseline Series (sometimes referred to as a Standard Series) alongside additional Specialist Series. The Baseline Series contains a selection of common haptens with high prevalence in a specific geographical region. For example, there is a British Standard Series that the leading patch test Specialist Dermatologists in Gt. Britain have agreed are the most important contact haptens for patients in GB. Similarly, there is a Swedish Baseline Series, a European Baseline Series, an Australian Baseline Series, a New Zealand Baseline series, no less than several different American Series, and so on. These different Series can range in number from just 20 different haptens to 90 haptens.
Specialist Series contains haptens that have high prevalence (frequency of occurance) in certain occupations, such as Paints, Adhesives, Dental, etc. There are also Specialist Series based on particular groups of chemicals found in the household, such as Cosmetics, Sun-Screens, Perfumes, Shoes, etc.
The Patient may be asked by the Dermatologist to provide samples of substances that the Specialist suspects may be the problem haptens from the patients own workplace or own home.
The combination of series (Baseline/Standard Series and/or Specialist Series and/or Patients own substances) will be determined by the Specialist, based on the specific patient history.
Diagnosis of Allergic Contact Dermatitis
The symptoms of a contact allergy such as itchiness, redness, and skin lesions can be treated, by steroid creams and other such pharmaceuticals, as well as by various natural products. However, the best treatment is avoidance of the problem substances that cause the Allergic Contact Dermatitis (ACD). The accurate and reliable identification of these problem substances is therefore an essential prerequisite.
Patch tests are used to identify the usually chemical substances that are causing the patient’s ACD, by mimicking the contact process in a scientific and controlled manner.
Over 550 different sensitising substances are known to cause ACD, though there are many more substances that have the potential to cause sensitisation and subsequent ACD.
The Dermatologist or Allergist will make a selection of which of these substances to utilise in a patch test, based on the patient’s individual circumstances, the clinical presentation, any suspicions based on their clinical experience, and on what patch test substances are available to them.
Most usually, there will be a standard test panel of haptens that is used for all patients with ACD. This may be as few as 20 different substances, or as many as 90 substances. That Baseline or Standard Series may be complemented by a Specialist Series of haptens that may be most relevant for the patient and their ACD. In addition, there may also be samples of haptens from the patient’s own workplace or home environment (such as chemicals, cosmetics, etc.).
Knowing what hapten is causing the ACD helps the patient avoid these haptens, thereby not invoking ACD and consequently effectively improving the quality of life for the individual.
Note that there is no equivalent or comparable in vitro blood test to identify haptens causing ACD in a particular patient.
Skin Prick Testing
Skin Patch Testing is not the same as Skin Prick Testing, which is used by Allergists to identify usually biological substances such as pollens and moulds and animal danders and foods, that can cause respiratory allergies and food allergies. This is known as a Type I Immediate Hypersensitivity reaction and involves the production and actions of IgE antibodies directed against the problem allergens. Skin Prick Tests are not to be used for any diagnosis of Allergic Contact Dermatitis.
Besides Skin Prick Tests, there are different in vitro lab-based tests on the patient's blood sample that can be used to identify the (usually biological) allergens to which a person is allergic.
These tests are known as s-IgE tests or RAST tests or the most recent development is the ALEX test (Allergy Explorer) that tests for 300 allergens and allergen components in one small blood sample.
To ensure that the hapten remains in direct contact with the skin for the time required (48 or 72 hours) to create a standardised controlled reaction, a Patch Test Chamber Strip is needed.
A Patch Test Chamber Strip is composed of sets of chambers mounted on an adhesive tape. The purpose of the patch test chambers is to provide a defined area in which the skin will be exposed to the haptens during the testing. Due to the nature of patch testing it is important that the Patch Test Chamber Strips used have good occlusion to the skin and that they are made of inert materials that do not interfere with the haptens tested.
The patch test chamber strips classically comprise 10 test sites, so for 10 patch test haptens.
The chambers and therefore also the hapten that is applied to the skin under the chamber, should ideally be square in shape so as to differentiate from any irrelevant skin condition that will be either round or irregularly shaped.
Consider that a Standard or Baseline Series may be 30 to 90 tests, plus a Specialist Series that may be of 10 to 40 tests, plus possibly also a few samples of the patient's own substances, then that will easily total 100 or more patch tests. This means 10 or more Chamber Strips to be affixed to the patient's back for a period of 48 or 72 hours.
The haptens are added to the chamber strip test sites in a logical and controlled order, so that any skin reactions can easily be assigned to specific haptens.
When the patches are affixed to the patient's back, their location is marked with a special pen so that after the patch test chamber strips have been removed, any reactions seen can still be allocated to specific haptens in a specific chamber strip.
Patch testing involves a number of scheduled patient appointments within a one-week timeframe. After the application of the patch tests on Day 0, two or sometimes three appointments are needed for readings of any reactions. The main reading should be performed at 48 hours or 72 hours, immediately after the removal of the Patch Test Chamber Strips. Another reading should be performed by the Dermatologist or Allergist a full week (Day 7) after the initial test application for haptens that may show delayed reactions. Only then after these readings of any reactions can the Specialist provide the diagnosis and confirm the identity of the problem substances, and discuss with the patient the future course of action to avoid the identified problem substances. This of course requires an in-depth knowledge of what substances are found in workplaces and in household products.
Occasionally, with some haptens, a very late reaction will develop, so after 7 days. Some substances are more likely to cause this than others. This reaction might be noticed by the patient, due to the itching. If this occurs, then it is recommended that the patient take a digital photograph of the reaction (not so easy!) and email that to their Dermatologist for them to include in the test results. This could possibly be a very significant finding. Ideally, the reaction site will still be identifiable by the location marks which will hopefully still be present on the patients back.
Patch Test Reactions
Normal Reactions:
In sensitised patients, exposure to haptens during the patch testing procedure will normally result in a miniature eczema (normal patch test reaction). In addition to the visual imprints on the skin from each chamber, a slight erythema from the frames should be visible as a sign of good occlusion. The erythema generally subsides within 30 minutes after removal of the Chamber Strips. The erythema may however prevail for up to 24 hours or more for patients with sensitive skin. Itching at the site of application of the Patch Test Units is not uncommon; it can either be caused by a positive patch test reaction or may occasionally be due to tape irritation. See the pic below.
Adverse Reactions:
A strong positive reaction may result in a flare-up of an existing, or sometimes a previous, dermatitis. Such flare-up reactions usually indicate that the responsible hapten is or has been, respectively, the cause of the dermatitis.
Sensitisation by patch testing is a rare but potential complication of patch testing. It is regarded as a positive patch test reaction generally 2 weeks after an initially negative response at the same patch test site. Rarely localised transient hyper-pigmentation or hypo-pigmentation may occur. A positive patch test reaction can rarely persist for up to several weeks.
Patients are instructed to report any side effects to the Specialist.
References for Further Reading
There are innumerable sources of information available to a person seeking knowledge and explanations on Allergic Contact Dermatitis, and other similar skin conditions, as well as on Patch Testing.
Of course, the best source is a Consultant Dermatologist, but that may be inaccessible, or expensive or inconvenient.
Online there are numerous good and reputable sources of information; most typically the websites of various professional medical societies for Dermatologists, as they provide a service not only to their member Dermatologists but also to Patients.
Suitable websites or webpages are recommended below for further reading.
1. https://dermnetnz.org/topics
New Zealand website for Dermatology Patients
2. https://www.dermcoll.edu.au/a-to-z-of-skin/
Australian website for Dermatology Patients
3. www.bad.org.uk / https://www.skinhealthinfo.org.uk/
UK website for Dermatology Patients
4. https://www.aad.org/public/diseases
American Academy of Dermatology Association
5. https://www.mayoclinic.org/diseases-conditions/contact-dermatitis/symptoms-causes/syc-20352742
Mayo Clinic webpages on Allergic Contact Dermatitis
6. https://www.healthline.com/health/contact-dermatitis
Healthline webpages on Allergic Contact Dermatitis
7. https://www.nhs.uk/conditions/contact-dermatitis/
UK National Health Service webpages on Allergic Contact Dermatitis
8. https://nationaleczema.org/eczema/types-of-eczema/contact-dermatitis/
Webpages of the National Eczema Association of USA on Allergic Contact Dermatitis
9. https://emedicine.medscape.com/article/1049216-overview
Webpages of eMedicine of USA on Allergic Contact Dermatitis
10. https://en.wikipedia.org/wiki/Patch_test#:~:text=A%20patch%20test%20is%20a,testing%20or%20skin%20prick%20testing .
Wikipedia article on Patch Testing
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