Contact Dermatitis- Patch Testing Techniques

Contact Dermatitis

If you have ever experienced dry, red or itchy skin, you know how frustrating and debilitating it can be.

Whether it is a small rash on your face or a rash covering your entire body, it is possibly due to Contact Dermatitis.

 

We recently attended the Melbourne Dermatology Conference in May 2019 and the Skin and Cancer Foundation patch test training day, where we got to learn more interesting information about Allergic Contact Dermatitis and refine our skill in patch testing. Patch testing is the way forward in allowing out patients to find out what they are allergic to!

Allergic Contact dermatitis (also called contact eczema) refers to a group of skin disorders in which the skin reaction is due to direct contact with the causative agent. The term dermatitis implies that the outside layers of skin are affected. It can be acute (a single episode) or chronic (persistent). Dermatitis is nearly always itchy.

Allergic Contact dermatitis is the most common cause of occupational skin disease, and is particularly common in cleaners, healthcare workers, food handlers and hairdressers due to the sheer numbers of chemicals these professionals come into contact with on a daily basis with work.

What does it look like?

  • Redness (erythema)
  • Blisters that are small (vesicles) or large (bullae)
  • Swelling (oedema)
  • Dryness or scaling
  • Cracks (fissuring)
  • Lichenification (thickened, lined skin)
  • Pigmentation increased (hyperpigmentation) or reduced (hypopigmentation).

What will patients complain of?

Itchy, dry skin in a patterned distribution. So for example, with hair dye allergy, it will come up as a scalp rash but also a rash and swelling around the eyes. For nail cosmetics allergy, this may come up as a rash around the eyelids. For allergies to clothing textiles and dyes, the rash might outline the exact pattern of the clothing (eg socks, gloves etc).

How is the diagnosis for contact dermatitis made?

The dermatologist will take you through a thorough consult, taking down all history carefully and making note of all possible irritants and exposures. Once the dermatologist can clearly identify what is causing your rash, it is important to avoid direct contact with those irritants.

  • Avoid soap – use a pH-balanced cleanser suitable for sensitive skin
  • Dry skin carefully after washing

The rash can be treated with a short course of topical corticosteroid steroid. Apply emollients/moisturiser frequently while the rash is active and for some weeks afterwards as the normal skin barrier function is restored. Severe contact dermatitis may be treated with a short course of systemic corticosteroids, e.g. oral prednisone. Occasionally, for chronic contact dermatitis, phototherapy may be tried, or immunosuppressive agents such as methotrexate,ciclosporin or azathioprine may be prescribed.

 

Patch Testing

If the dermatologist can’t determine the exact cause of your dermatitis straight off sometimes we have to do a bit of detective work to get to a diagnosis, that’s where patch testing comes in!

 

Patch testing is a simple and non-invasive way of detecting what your body is allergic or reacting too. We are looking for a diagnosis to help narrow down how your skin reacts to certain stimulants when placed on your skin for a certain amount of time. The first appointment will be a history taking exercise and thorough examination to narrow down potential allergens.

 

After the allergens for patch testing are then ordered (which can take 1-2 weeks), we will bring you back for an appointment to place allergen strips on your back. You will then come back 48 hours later to have your first reading; the second reading will be a further 48hrs to see if you have had a late reaction. Hence, we find doing a Monday-Wednesday-Friday cycle the most efficient way of conducting the readings.

 

We do a very thorough testing and can test for a range of different irritants such as

-Sunscreens                     -Airborne Allergies                -Tapes/dressings

-Fragrances                     -Textile dyes                          -Metals/nickel

-Cosmetics                     -Corticosteroids                     –Car Fragrance/air fresheners

-Hairdressing products

 

Once we get a diagnosis, we can then look at removing these from your routine and start treatment for you. These results can be positive OR negative, all leading to a diagnosis. If not allergic contact dermatitis then possibly irritant contact dermatitis could be the diagnosis.

Just remember to be patient, it is a process to get to a diagnosis, but it can be life changing once we get a diagnosis for you!

To start your skin journey and for patch testing appointments with one of our dermatologists please call our clinic on 9039 5644.

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