How dermatology patients become detectives

I recently attended the National Eczema Society’s day to celebrate Eczema Week. One of the presentations discussed skin allergy and allergy testing in particular.

The speaker asked the audience if any of them had had patch testing and if they had a positive result did they now know what they were allergic to.

I was amazed to see that not all had been given information relating their specific allergens and were not clear what they were and the other names for the same allergen.

Patch testing is indicated if allergic contact dermatitis is suspected (type IV hypersensitivity – also known as cell mediated or delayed type hypersensitivity occurring 48-72 hours after contact).

It involves the reproduction under the patch tests of an allergic contact dermatitis in an individual sensitised to a particular antigen(s).

The standard method involves the application of antigen to the skin at standardised concentrations in an appropriate vehicle and under occlusion for 48 hours before removal with a final reading at 96 hours.

There is a standard series of allergens tested with additional ones based on the clinical assessment and history (Johnston et al 2017). Following the test patients are given information regarding their specific allergens so they can then avoid them.

This detective role then becomes a challenge. I have been patch tested and know I am allergic to limonene, linalool (fragrances) and mercury and despite having my dermatology knowledge, I also have to become a detective both for my self and also my patients.

For example, limonene and linalool are in toothpaste (see resources) but not all toothpastes are listed so it means looking at the labels and contacting the manufactures for clarification of their products or looking for alternatives.

Some products are clearly labelled with the list ingredients and for others it is not always that clear. This includes products used on a daily basis such as cleaning products, shampoos etc. and medications purchased OTC (over the counter) or prescribed.

As healthcare professionals we need to ensure we signpost our patients and families to information they can use.

After patch testing patients are given information on the allergen(s), also highlighting different names for the same allergen, its sources and how to avoid it backed up with written or online information appropriate to their level of understanding.¹

Interestingly my observations at the eczema event are reflected in a study, which showed only 29% (41/141) patients remembered the name of the allergen after 10 years although 79% (111/141) of patients recalled having had a positive patch test result.²

So I challenge you to take one of the allergens listed in the standard series Appendix 1 in the BAD guidelines, can you identify the allergen at home or when you go shopping? Yes, it is a daily challenge for our patients and their families.

References

1. Johnston, G.A., Exton, L.S., Mohd Mustapa, M.F., Slack, J.A., Coulson, I.H., English, J.S.C. and Bourke, J.F. British Association of Dermatologists’ guidelines for the management of contact dermatitis 2017. Br J Dermatol, 176: 317–329. doi:10.1111/bjd.15239: http://www.bad.org.uk/shared/get-file.ashx?id=4375&itemtype=document
2. Jamil WN, Erikssohn I, Lindberg M. How well is the outcome of patch testing remembered by the patients? A 10-year follow-up of testing with the Swedish baseline series at the Department of Dermatology in Orebro, Sweden. Contact Dermatitis 2012; 66:215–20

Resources

• What are the excipients in toothpastes? www.ukmi.nhs.uk/filestore/ukmias/nwqa357.2whataretheexcipientsintoothpastes.doc
• electronic Medicines Compendium (eMC): https://www.medicines.org.uk/emc/ Summaries of Product Characteristics (SPCs) lists the excipients which I signpost patients to.
• European Union – Labeling/Marking Requirements https://www.export.gov/article?id=European-Union-Marking-Labeling-and-Packaging-Overview