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.
WHICH DOCTOR ?
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.
ALLERGIC CONTACT DERMATITIS
Contact allergy is the state of being sensitised to a hapten.
What is a Hapten, you may ask!
Essentially, a Hapten is a substance, usually a chemical, that when it becomes presented to the immune system of a person, usually through physical contact with that person, then the hapten becomes conjugated (attached) to an immune cell in a persons body, and this complex 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 a hapten.
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.
Do not confuse this "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., that usually cause respiratory reactions or gastro-intestinal reactions. These are identified usually by Skin Prick Tests (not Skin Patch Tests) or by blood tests to identify allergen-specific Immunoglobulin E (IgE).
Unfortunately many Family Practitioners/Primary Care Practitioners are too. That is why the involvement of a Specialist Dermatologist or Allergist is advised whenever possible.
For further information, please see the list of recommended reading at the end of this section on Patient Information.
Contact allergy is the result of specific immune responses caused by antigens, which are most usually chemicals. Unlike allergens (such as pollens and animal proteins) causing other forms of allergy, the culprits of Contact Allergies, haptens, are not antigens by themselves. 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 epidermal and dermal proteins forming “hapten-carrier complexes” with antigenic properties capable of causing contact allergy. Examples of widely recognised haptens include nickel, formaldehyde and preservatives in cosmetics.
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 encountering a hapten, others withstand a life-time of exposure 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 run a higher risk of developing ACD.
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.
PATCH TESTING CONCEPT
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 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.).
Note that there is no equivalent or comparable in vitro blood test to identify haptens causing ACD in a particular patient.
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.
Knowing what hapten is causing the allergic reactions helps the patient avoid these haptens, thereby not invoking ACD and consequently effectively improving the quality of life for the individual.
PATCH TEST PROCEDURE
In order to perform a diagnostic Patch Test, two crucial components are required:
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 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. 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.
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.
The hapten preparations used in patch testing should ideally be specifically developed for patch testing purposes.
The Patch Test Haptens manufactured by Chemotechnique 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 haptens to 90 haptens.
Specialist Series contains haptens that have high prevalence (frequency of occurence) 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.
To ensure that the hapten remains in direct contact with the skin for the time required (48 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 chambers and therefore 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 tests. This means 10 or more Chamber Strips to be affixed to the patient's back for a period of 48 hours.
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, 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.
Patch Test 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 due to tape irritation.
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.
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.
New Zealand website for Dermatology Patients
Australian website for Dermatology Patients
American Academy of Dermatology Association
Mayo Clinic webpages on Allergic Contact Dermatitis
Healthline webpages on Allergic Contact Dermatitis
UK National Health Service webpages on Allergic Contact Dermatitis
Webpages of the National Eczema Association of USA on Allergic Contact Dermatitis
Webpages of eMedicine of USA on Allergic Contact Dermatitis
Wikipedia article on Patch Testing