Section 4.0 Making An Initial Diagnosis

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 chemicals, water and skin contactants such as gloves and skin cleansers. The table below highlights the type of questions that a patient with contact dermatitis should be asked by the doctor. These questions form a large basis of the PatchCams, our clinic management database program used in all the SCF patch testing clinics.

Features of presenting complaintQuestions
SiteWhere 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?
SymptomsIs it itchy?
OnsetWhen 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 courseHow long have symptoms been present for? Is the rash intermittent or persistent?
MorphologyWhat is the nature of the rash? Does the description sound eczematous?
Aggravating factorsAre there any exposures or factors that make the rash worse? Do particular tasks at work or at home exacerbate the condition?
Relieving factorsWhat has the patient found improves their rash?
Response to treatmentWhat treatments have been tried and have they helped? Were oral corticosteroids required?
Work relatednessDoes time away from work help? How long does it take to improve?
Associated featuresHas the patient experienced any breathing difficulties, lip or tongue swelling?
SeverityA 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.

Adapted from 6

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. Knowledge of potential allergens is essential to direct appropriate patch testing. It is also important to document exposures to skin irritants. 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 of course overlap. Careful questioning is needed about all exposures. It may be useful to obtain photos of workplace – consider processes undertaken, chemicals or items handled, personal protective equipment used etc. or material safety data sheets/ product labels.

Personal exposuresHand washing – frequency denoting wet work exposure, 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
Body washing – frequency, soaps, liquid soaps
Moist wipes such as baby/toilet wipes and make-up wipes
Shaving cream
Moisturizers – frequency, type
Topical medicaments
Use of reusable or disposable gloves at home
Hobbies: gym gloves, paints, glues, mechanical work etc.
Occupational exposures

Which substances does the patient handle at work?

Safety data sheets for work products may need to 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 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 contact dermatitis.
  • Dermatological 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


Talk to the patient 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.
  • Is the patient on any immunomodulatory or oral corticosteroids which may impact patch testing?


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 such as to nickel, fragrance and sticking plaster. It is suspected that individuals with known allergic contact dermatitis are more likely to develop further contact allergies7.


A smoking history may be associated with an increased risk of hand eczema, and possibly also severity8.


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. Common sites for contact dermatitis are discussed below.

Clinical examination and morphology

  • Is this an eczematous rash or not?
  • Non-eczematous rashes include psoriasis, tinea, granuloma annulare, porphyria cutanea tarda
  • If rash is eczematous, the possible diagnoses include endogenous types of eczema AND all forms of contact 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

Refer to patch testing guide on site of rash – see attachment

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.


There are a limited number of medical investigations that may be used when diagnosing or eliminating contact dermatitis. Listed below are the most common investigations used.

Patch testingIt is important to patch test all individuals with a persistent eczematous skin condition, to exclude the possibility of allergic contact dermatitis. 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.
Blood (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 generally considered to be a safer option as opposed to prick testing when testing for latex allergy.

Consider testing other specific IgE levels if there is a good history of immediate reactions to a certain allergen such as certain foods (particularly for food handlers), house dust mite and animals.

Total IgEAlthough not a diagnostic test, it 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. In our experience, people with atopy and a very high IgE are more likely to require more aggressive therapy for their condition.
Repeated open application test (ROAT)This is not routine, yet can be a useful adjunct to patch testing. Test substances are applied to the same area of skin twice daily for seven days, or until a reaction occurs if prior to seven days. It can be of particular help in clarifying doubtful and weak, yet suspicious, patch test reactions. It may assist in confirming whether a specific product contains a reagent in a sufficient enough concentration to elicit ACD. See information sheet for further information or
Skin prick testingThis is used to diagnose contact urticaria along with blood serum tests. Should be considered if the clinical presentation is consistent with an immediate reaction and is particularly important when allergens are not available for blood tests. On the other hand, there is a lack of standardization regarding the concentration used for testing many contact urticants.
Testing for non-immunologic contact urticariaThis 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 scrapingsConsider with scaly dermatoses of the hands or feet to exclude fungal infection.
Skin biopsyIf 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 reliable in differentiating between an endogenous and exogenous cause of dermatitis.

Adapted from 6

Don’t forget to consider immediate hypersensitivity or Type 1 reactions

  • Common causes include natural rubber latex, foods, ammonium persulfate (hairdressing bleach)
  • Less commonly, inhalant allergens: house dust mite, animals Malassezia, furfur, chlorhexidine
  • Presents with immediate burning, redness: contact urticaria
  • Repeated episodes may cause protein contact dermatitis
  • Tested by blood test or prick testing, NOT by patch testing. Allergists perform prick testing, except some dermatology nurses may be trained to perform this testing.

Consider latex allergy

  • In the past, disposable latex gloves had high amounts of latex protein – this has gradually reduced over time
  • Glove powder (corn starch) found to facilitate latex allergy
  • Powdered disposable gloves are still main cause of latex allergy
  • Highest rates of latex protein in products like balloons
  • Reusable rubber gloves are associated with approximately 15% of our cases with latex allergy, so latex allergy should still be suspected in those wearing reusable rubber gloves or non-powdered disposable gloves
  • In the clinical setting, 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)
  • 27% of people with latex allergy had facial rash, 4.3% had a generalized rash4.

Videos to watch

Patch test live 1-3 videos and notes

Scroll to Top