History of presenting complaint
Taking a thorough history is vital when deciding which allergens or series to test. Consideration should be given to exposures such as skin cleansers, gloves and chemicals. Table 1 highlights the type of questions which the dermatologist should be asking the patient during a patch testing consultation. These questions form the basis of PatchCams©, our clinic management database program used in all the Skin Health Institute patch testing clinics.
The information in table 1 and 2 has also been published in the 2014 edition of “Patch testing tips: Recommendations from the ICDRG,” in a chapter written by Associate Professor Rosemary Nixon and Dr Ryan Toholka.
Table 1 – Presenting Complaint
| Features of presenting complaint | Questions |
| Site | Where did the rash start? This may give a clue as to the nature of the initial allergen. Did the rash spread subsequently? What areas of the body are affected by the rash? |
| Symptoms | Is it itchy? |
| Onset | When did the rash start? Are there any new exposures that the patient can associate with development of the rash? How long after the exposure did the rash start? |
| Time course | How long have symptoms been present for? Is the rash intermittent or persistent? |
| Morphology | What is the nature of the rash? Does the description sound eczematous? |
| Aggravating factors | Are there any exposures or factors that make the rash worse? Do particular tasks at work or at home exacerbate the condition? |
| Relieving factors | What has the patient found improves their rash? |
| Response to treatment | What treatments have been tried and have they helped? Were oral corticosteroids required? |
| Work relatedness | Does time away from work help? How long does it take to improve? Does the skin improve when on holidays? |
| Associated features | Has the patient experienced any breathing difficulties, lip or tongue swelling? |
| Severity | A rating system out of 10, scored by both patient and doctor, can help to assess relative severity. The rash may have improved prior to assessment. It also aids in monitoring progress at future visits. |
Exposure history
When considering the diagnosis of contact dermatitis, it is important to accurately determine all of the substances that come in contact with the patient’s skin as demonstrated in Table 2. Knowledge of potential allergens is essential to direct appropriate patch testing. It is also important to document exposures to skin irritants, even handwashing with water. Remember that the causative allergen may not necessarily be a new exposure: allergies can start at any stage.
Exposures may be classified as personal and occupational and may overlap. Careful questioning is needed about all exposures. It may be useful to obtain photos of the workplace – consider the processes undertaken, chemicals or items handled, personal protective equipment used and the potential for skin exposures.
Table 2 – Exposure History
| Personal exposures | Hand washing – especially the frequency, soaps, liquid soaps, hand cleaners |
| Hair products – shampoo, conditioner, dyes, gels, waxes, sprays | |
| Make up – facial products, eye and lip products, nail products – acrylic nails, nail polish | |
| Fragrances – colognes, perfume, deodorants, fragrance diffusers, oil burners, air fresheners and essential oils | |
| Body washing – frequency, soaps, liquid soaps | |
| Sunscreens | |
| Cleansing wipes such as baby/toilet wipes and make-up wipes | |
| Shaving cream | |
| Moisturisers, serums, anti-ageing preparations | |
| Topical medicaments | |
| Use of reusable or disposable gloves at home | |
| Jewellery | |
| Hobbies: gym gloves, paints, glues, mechanical work, gardening | |
| Occupational exposures |
Which substances does the patient handle at work? Safety data sheets for work products should be reviewed to see if they contain allergens or irritants. |
| What personal protective equipment (PPE) is used? Is it always used? | |
| Have there been times when there has been an accidental spill of chemicals or PPE has failed? | |
| What types of gloves are used? Disposable or reusable? Powdered? How often? For what tasks? | |
| Which substances may be airborne? | |
| What is the work environment like – is it dusty, hot/cold, wet? Is there appropriate ventilation? | |
| Has anyone else at work had skin problems? |
Past medical history
- Atopy: This includes atopic eczema (dermatitis) and/or asthma and/or hay fever. There are many definitions but essentially the determination of atopy involves establishing a background of atopic eczema, and/or asthma and/or hay fever. Atopy is a known risk factor for occupational irritant contact dermatitis
- Skin conditions
- Other medical/surgical conditions
Family history
- Atopy: family history is an important risk factor for a person developing atopic eczema; this could be as high as 50% if both parents have an atopic history
- Psoriasis
Medications
Ask about current and past medications:
- Consider medications used for the treatment of skin conditions, including both topical and systemic treatments
- Other medications used for non-skin related conditions
- Have there been any new medications, which may have coincided with the development of the patient’s skin condition?
- Don’t forgot to give consideration to non-prescription medications, natural remedies, herbs and vitamins
- Is the patient on any immunomodulatory treatment or oral corticosteroids which may impact patch testing?
Allergies
Ask about allergies to medications, food and immediate reactions such as animal, pollen and house dust mite allergy. It is also important to question the patient about a history of contact allergy to common allergens such as to nickel, fragrance and sticking plaster. People who have reacted to multiple allergens may be at more risk of future reactions (polysensitisation).
Smoking
A smoking history may be associated with an increased risk of hand eczema.
Examination
A thorough skin examination can give valuable clues to a patients’ diagnosis. It is important to always consider the relationship between the site of dermatitis and particular exposures.
Clinical examination and morphology
- Is this an eczematous rash or not?
- Non-eczematous rashes on the hands include psoriasis, tinea, granuloma annulare, porphyria cutanea tarda
- Non-eczematous rashes on the face include rosacea
- If rash is eczematous, the possible diagnoses include endogenous types of eczema AND all forms of contact dermatitis
- Eyelid dermatitis is very suggestive of allergic contact dermatitis, although can also occur in atopic eczema (dermatitis)
- Cannot differentiate the causes of contact dermatitis clinically
- Vesicles do not necessarily mean pompholyx (endogenous hand eczema)
- Contact urticaria may resolve completely or may evolve into protein contact dermatitis
Please refer to Patch Testing Guide on Site of Rash for more information on common sites for contact dermatitis.
It is important to note that an individual can sometimes have a combination of skin conditions occurring concurrently (or multiple diagnoses), which can make the diagnostic process complicated.
Investigations
There are a limited number of medical investigations that may be used when diagnosing or eliminating contact dermatitis. Table 3 lists the most common investigations used.
Table 3 – Investigations
| Investigation | Considerations |
| Patch testing | It is important to patch test all individuals with unexplained eczematous skin condition, to exclude the possibility of ACD. Patch testing should include the Australian Baseline Series, then additional specific allergens or series, depending on exposures. Patients’ own samples should also be tested, ensuring they are appropriately diluted. |
| Serum-specific IgE tests |
Latex – This is important if the patient has any exposure to latex. Patients wearing reusable, not just disposable, gloves may develop latex allergy. A blood test is safer and more convenient option as opposed to prick testing when testing for latex allergy. Consider testing other specific IgE levels if there is a history of immediate reactions to allergens such as certain foods (particularly for food handlers), pollens and animals. Useful IgE test in facial dermatitis include to house dust mite and Malassezia in patients with a seborrheic dermatitis phenotype. |
| Total IgE | Although not a diagnostic test, a total IgE can be helpful in assessing a patient’s atopic predisposition. This is important in the diagnostic pathway for a patient and may assist with the future direction of treatment. Generally, people with atopic eczema (dermatitis) and a very high IgE are more likely to require more aggressive therapy for their condition. |
| Repeated open application test (ROAT) | This can be a useful adjunct to patch testing. Test substances are applied to the same area of skin twice daily for approximately ten days, or until a reaction occurs if prior to ten days. It can be of particular help in clarifying doubtful, yet suspicious, patch test reactions. It may assist in confirming whether a specific product contains an ingredient in a sufficient enough concentration to elicit ACD, when the product containing a known allergen yet has not reacted. This will be covered in Section 7.4 Repeated Open Application Test |
| Skin prick testing | This is used to diagnose contact urticaria, along with serum tests. Should be considered if the clinical presentation is consistent with an immediate reaction and is particularly important when serum specific IgE tests are not available. However, there is a lack of standardisation regarding the concentration used for testing of non-standard allergens |
| Testing for non-immunologic contact urticaria | This is an open test, where a small amount of a test substance is applied to the volar aspect of intact skin of the forearm for 30-45 minutes. |
| Fungal scrapings | Consider scraping scaly dermatoses of the hands or feet to exclude fungal infection, especially when unilateral. |
| Skin biopsy | If the morphology of the rash does not clearly indicate an eczematous process, a biopsy can help in the diagnostic process. A biopsy however is not always reliable in differentiating between an endogenous and exogenous cause of dermatitis, although generally ACD will feature more eosinophils. |
Don’t forget immediate hypersensitivity or type 1 reactions
- Common useful serum tests include natural rubber latex, chlorhexidine and Malassenzia furfur. However, there is no serum test for ammonium persulfate.
- Inhalant allergens when relevant such as house dust mite, animals, grasses and pollens
- Foods when relevant, particularly wheat and rye in bakers
- Contact urticaria presents with immediate burning and redness, and maybe hay fever
- Repeated episodes may cause protein contact dermatitis
- Tested by blood test or prick testing, NOT by patch testing. Trained allergy and dermatology nurses can perform prick testing.
Consider latex allergy
- In the past, disposable latex gloves contained high amounts of latex protein. However, this has gradually reduced over time with improvements to the manufacturing process.
- Glove powder (corn starch) was found to facilitate latex allergy by transferring latex from the powdered glove to the skin
- Powdered disposable gloves are still the main cause of latex allergy
- Highest rates of latex protein are found in products like balloons
- Reusable rubber gloves are associated with approximately 15% of our cases of latex allergy, so latex allergy should still be suspected in those wearing reusable rubber gloves or non-powdered disposable gloves
- We have also reported that 52% of people with latex allergy worked outside healthcare and were using latex gloves inappropriately (i.e. when they could be wearing non-latex gloves)
- And finally that 27% of people with latex allergy had facial rash and 4.3% had a generalized rash
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