Many factors can contribute to a patient’s skin condition. Contact dermatitis may only be one factor. Approximately 47% of patients assessed in our Occupational Dermatology Clinic at SHI, Melbourne are found to have more than one diagnosis e.g. irritant contact dermatitis (ICD), allergic contact dermatitis (ACD), with underlying atopic dermatitis.
Some people may NOT actually be diagnosed with ACD following patch testing, but it is important to exclude this diagnosis with thorough and appropriate patch testing. For example, young adult patients with endogenous hand eczema (also called pompholyx, dyshidrotic eczema, vesicular hand dermatitis), often experience aggravation from irritants when working in hospitality, however ACD from hand cleaners or gloves often needs to be excluded.
Differential diagnoses for hand dermatitis may include:
- Irritant contact dermatitis
- Allergic contact dermatitis
- Contact urticaria/protein contact dermatitis
- Endogenous forms of eczema: Hand eczema, atopic eczema, rarely discoid eczema
- Psoriasis
- Infection e.g. tinea, bacteria
- Porphyria cutanea tarda
- Glove-related hand urticaria
By the end of the patch testing process, all patients should be given a diagnosis of their skin condition, which will be partly subjective and partly objective, based on the dermatologist’s assessment. Use of the flow chart “Understanding your skin condition” developed by Associate Professor Rosemary Nixon (Figure 1) can help the patient understand their diagnosis (or multiple diagnoses), and how patch testing fits in to their diagnostic journey.
At the SHI, we find it useful to commence the education process at the day 2 reading, before the patch testing process has been completed, so the patient really understands what is going on. Giving patients initial information about any positive tests after day 2 helps to engage patients in the search for relevant exposure to allergens. The flow chart is discussed with patients again at the conclusion of testing on day 4 (after final patch test readings).
Additionally it is important for patients to be aware that late patch test reactions are possible and may occur up to 10 days after patch testing. It is important to mention this to patients at their final appointment, and to give instructions about what to do if a late reaction occurs. The patient should be advised to phone the clinic and if possible, email a photo of their back. They may need to return to the clinic for the dermatologist to review their reactions.
Remember, general practitioners and other health care professionals such as pharmacists, may have a limited understanding of delayed hypersensitivity, so it is essential that the patient understands what they have been diagnosed with as well as the relevance of any positive patch test results and what that means for them on a day-to-day level.
Example cases
Example 1
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A young woman presented with axillary dermatitis caused by fragrance in her deodorant, confirmed by a positive patch test reaction to fragrance mix and a positive patch test to her deodorant (tested ‘as is’). She also reacted to nickel, and has a history of having dermatitis some years ago from cheap earrings, likely to have contained nickel. Her reaction to nickel was therefore classified as old or past relevance. Diagnosis ACD to fragrance, current relevance Contact allergy to nickel, past relevance It is important to record the fact that the patient reacted to nickel, because she may develop contact dermatitis in the future, such as when wearing a white gold ring, which may contain nickel. However because she does not demonstrate a clinical history of nickel ACD currently, we classify this as ‘contact allergy”, not ACD. |
Example 2
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A nurse with a background of childhood atopic eczema developed steadily worsening hand dermatitis in the context of her work, with improvement on holidays. She usually wears nitrile gloves, except with for sterile procedures when she wears powdered latex gloves. She washes her hands with the hospital skin care cleanser. She blamed an alcohol hand rub. Patch testing revealed a positive reaction to coconut diethanolamide which was present in the hospital skin cleanser. A serum test was positive to latex. Diagnoses ACD to coconut diethanolamide in skin care cleanser. Latex allergy caused by wearing powdered latex gloves. Likely contributing ICD (diagnosed subjectively on history) from wet work. Generally alcohol rubs are associated with less ICD, because of less water exposure and less use of paper towels. Background of atopic eczema which means that she is likely to have more easily irritated skin. |
In summary
When finalising a patient’s diagnosis at the conclusion of patch testing, there are a few things to consider. Firstly, it is important to list the relevance of each positive patch test reaction: current, old or unknown.
If tests are negative, consider other possible causes. The most common causes will be endogenous forms of eczema. However, other possibilities include immediate reactions. Do you need to perform prick or serum tests? Has an allergen been missed or is repeat testing required to corroborate a reaction? Testing of metals can be particularly problematic, and repeating tests is often helpful. In our prosthetic joint series, we have in-built duplicates of important metals.
Patch testing is valuable in making a diagnosis, but it is also important to recognise the possible role of skin irritants and immediate hypersensitivity. Most people should leave their final appointment with a diagnosis or a diagnosis for their skin condition. Their skin condition may in fact be atopic eczema, but the patient and their treating practitioner can be reassured that ACD to their skin care treatments and topical therapy has been excluded on patch testing. To make a diagnosis of ACD there needs to be a compatible history of dermatitis, a positive patch test and evidence of exposure to that allergen.
Common mistakes of the novice patch tester
- To assume all positive patch test reactions are relevant. The most likely positive and non-relevant reaction is to nickel
- To underestimate the role of ICD: consider exposure to irritants as well as allergens
- There is no diagnostic test available for ICD: it is often a default diagnosis and is subjective
- With treatment, remember to emphasise skin protection and skin care measures as well as allergen avoidance
- Ignore the role of immediate hypersensitivity reactions
Patch testing diagnostic flow chart
We use the following algorithm to assist in making a diagnosis of the patient’s skin condition, and to explain the diagnostic process to patients. The features of the algorithm include the fact that the positive reactions do not necessarily lead to the diagnosis as they may not be relevant to the patient’s skin condition.
The algorithm also incorporates ICD, which is always an important differential diagnosis of ACD, and may co-exist with ACD. It also includes immediate reactions, as many patients are confused about what is tested by prick testing and what is tested by patch testing.
Finally, there are multiple lines for the diagnosis; there may be multiple contributing factors to the patient’s condition. It is not uncommon for a patient to be allergic to an ingredient of a hand cleanser used at work, have an atopic background with a element of ICD as well. All of these factors need to be addressed to effectively treat the dermatitis.
Figure 1 : Understanding Your Skin Condition Flow Chart
In addition to explaining the patient’s diagnosis, it is important to emphasise management. Management depends on the diagnosis, however providing advice on skin care, glove use and reduction or elimination of relevant exposures is also crucial. Patients may not have been told to moisturise their hands by their referring practitioner but not done so.
Managing the risk using the hierarchy of control
Occupational contact dermatitis can be addressed by following the Hierarchy of Control developed by the Occupational Health & Safety Administration, where action is required at multiple levels
https://www.osha.gov/sites/default/files/Hierarchy_of_Controls_02.01.23_form_508_2.pdf
Priority 1: Elimination
- Removal of the cause of the problem if possible. It may be possible to eliminate use of a particulat irritant or allergen.
Priority 2: Substitution
- Replace the substance or activity with one of less harm, such as using a less irritating soap substitute, or a product with less allergens.
Priority 3: Engineering
- Introduction of engineering controls to change the way a task is done, such as using a dishwasher in a kitchen vs handwashing dishes
Priority 4: Administration
- Introduction of policies and procedures for safe handling of substance. Using rostering to decrease exposures, such as avoiding more than 2 or 3 consecutive shifts.
Priority 5: Personal protective equipment
- Considered the last resort in order to protect workers from hazards in their workplace, and can include gloves, gowns, aprons, masks.
Allergen avoidance
If there are relevant positive reactions it is important to provide information on the allergen and how best to avoid it.
This should comprise of:
- Written Information including allergen name (including any synonyms), typical uses and where it is commonly found and how best to avoid the allergen. The team at SHI, have developed information sheets for use in the patch testing clinic. These are available on the PatchCams© website www.patchcams.asn.au. Additionally information sheets about individual allergens are also available on the allergEAZE® website http://allergeaze.com/ and Chemotechnique website www.chemotechnique.se
- Information sheets can also be emailed directly to patients from PatchCams© or printed and given to the patient. A video about how to do this is available on PatchCams©
- Advise the patients to check all their products for the relevant allergen. The CosMe© app is a good way to learn how to avoid products containing known allergens for the patient and find safe products that can be used. You can learn more about this app here.
- Explaining the allergy cannot be treated with desensitisation therapy and will likely be lifelong. Desensitisation is only available for certain immediate hypersensitivity reactions e.g. pollens, grasses etc, performed by allergists.
Patient education and resources
Once a patient has their patch test results, giving them information about what they can and can’t use at work and at home is important in healing their skin. It can be very tricky for the patient to remember the allergen and chemical names, as one allergen can have several different names. It is best to give written information to the patient to they remember what they are allergic to. Patients do need to become label readers of all products so avoid contact with the offending allergen.
The allergen manufacturers provide information sheets on all allergens they manufacture. These are available on their websites www.chemotechnique.se and www.smartpracticecanada.com They are also available via PatchCams© as they have been matched with all the series and allergens listed in the program. They can be printed or emailed directly to the patients from PatchCams©, click here to learn how. SHI have also written local information sheets, with Australian specific information and products and focuses on our local experience in Melbourne.
The CosMe© app has been a welcome addition to the patch testing education tools, it is a growing database of products with options for personalisation about what products a person can or cannot use, following their patch testing. More information about this can be found by clicking on the CosMe© flyer or watching the CosMe© video.
Videos to watch
