Allergic contact dermatitis is a form of dermatitis/eczema triggered by an allergic reaction to an allergen (material) contacted with the skin. Usually, the allergen appears quite harmless to the rest of the population. 

Typically, allergic contact dermatitis affects the general population, but can also be prevalent in certain employment groups. It is more common in women than in men, primarily due to nickel allergy and acrylate allergy, which is associated with nail cosmetics. Many children also have nickel allergy. Patients over 70 years old experience contact allergy from topical antibiotics.

Health care workers, cleaners, hairdressers, metal workers, painters, and florists are employment groups in which the rate of allergic contact dermatitis is relatively high.

Allergic contact dermatitis is classified as type 4 or delayed hypersensitivity reaction that occurs within 48-72 hours after being exposed to the allergen. CD4+ T-lymphocytes that are responsible for recognizing an antigen on the skin surface, release cytokines that eventually activate the immune system and cause dermatitis as a result.

It is important to note that patient may be in contact with an allergen for several years and remain asymptomatic until a certain time period. Contact even with tiny amounts of an allergen can facilitate dermatitis.

Patients who have impaired skin barrier function including those with chronic irritant contact dermatitis and leg ulcers are more prone to allergic contact dermatitis.

As previously mentioned, allergic contact dermatitis arises a few hours after an individual came in contact with allergen. Usually, it occurs on the contact site; however, in some cases, allergic contact dermatitis can go beyond the contact area or become generalized. For instance, transmission from fingers can facilitate dermatitis on eyelids. The affected skin may appear red, itchy, swollen, blistered, dry and/or bumpy.

The most common examples of allergic contact dermatitis include the following: reactions to fragrances in perfumes and household items; contact with jewellery items, hair dye due to allergy to paraphenylenediamine, rubber gloves due to rubber accelerator chemicals, dental implants with acrylates, etc.

Allergic contact dermatitis usually starts as a localized reaction to an allergen that had contact with a skin. However, allergic contact dermatitis can generalize due to autoeczematisation and result in erythroderma.

In some cases, contact allergy can occur in the form of photocontact dermatitis which occurs after exposure to ultraviolet (UV) light.

In terms of diagnosis, allergic contact dermatitis can be easily identified and no further tests are needed. It is necessary to collect patient’s history regarding work environment, products used at home, products used at work, sun exposure, and hobbies.

The open application test may be performed to confirm contact allergy to a cosmetic product (e.g. moisturizer). The product has to be applied several times throughout the day for a few days in a row on a small area of sensitive skin.

Patch testing is done in dermatology clinics and is highly recommend for patients who have suspected contact allergy, especially if the reaction is chronic, severe, or recurrent. The purpose of these tests is to determine which allergen causes the rash.

The key step for treating allergic contact dermatitis is to find how you contact an allergen and avoid contact with it in the future, if possible. With a help of patch testing, the patient finds out the specific allergens they are allergic to and are given a list of products to avoid. It is also suggested to wear appropriate gloves that will protect hands from coming into contact with the allergen.

Active dermatitis is usually treated with topical steroids, emollient creams, oral steroids for short courses, phototherapy, or immunosuppressive agents.

Contact allergy usually lasts a lifetime; however, it can be reduced by knowing the exact allergen(s) and avoiding them. Dermatitis can re-occur if an individual will remain in contact with allergen or resume the contact. Overall, prognosis highly depends on patient’s compliance and knowledge of allergens as well as appropriate skin care.

Centre for Medical and Surgical Dermatology offers unique and personalized allergic contact dermatitis treatment options for each patient. 

For more information about patch testing, visit the following link: