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Allergic Contact Dermatitis


Allergic contact dermatitis is a form of a rash or eczema caused by a delayed allergic reaction to an allergen – most commonly a metal, fabric, plants, rubber, topical medicine and cosmetics. It is not contagious.

Allergic contact dermatitis is very common in the general population worldwide, especially in employment groups which are naturally exposed to specific allergens, like beauticians, painters, florists as well as healthcare, and metal workers. Allergic contact dermatitis affects people of all ages, though within the adult population, it is more likely to occur in women than in men. Patients with impaired skin barrier function e.g. suffering from atopic dermatitis, are especially prone to acquiring the condition.


Allergic contact dermatitis is caused by a delayed type of allergic reaction, known as a type 4 hypersensitivity reaction. In this case, the immunological response typically \occurs approximately 48 – 72 hours after the exposure to the allergen. CD4+ lymphocytes are a type of white blood cell. These lymphocytes are responsible for presenting an antigen, a foreign body that evokes an immune response, to the immune system. If the patient is exposed to the allergen for the first time, the symptoms might show up to 14 – 21 days afterwards and present mildly, if at all. However, with subsequent exposures, the reaction may appear faster, and with a more robust response.


In the acute phase of allergic contact dermatitis, the lesions take the form of intensively itchy vesicles, accompanied by erythema and oedema. They can also resemble chronic, itchy, erythematous dermatitis. At the beginning, they are strictly limited to the exposition site, nonetheless, if the acute phase progresses into a chronic condition, they might exceed the contact surface. What is often common in allergic contact dermatitis caused by plants is that the lesions arrange themselves in a linear manner. Overall, the disorder most frequently affects the skin of the face, the hands and the forearms – the body parts most exposed to potential allergens.
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  • Undergo a patch test to determine the exact allergen that is causing the reaction.
  • Having identified an allergen, avoid contact with it by taking appropriate protective measures e.g. wearing protective clothing or carefully reading an ingredient list before buying a product.
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First choice treatment in allergic contact dermatitis is topical steroids for 2 – 3 weeks, combined with limited use of other topical products including cosmetics. Most often, a simultaneous emollient therapy is incorporated to provide the best care to the affected skin, preventing any possible exacerbation. In more severe or extensive cases, a 3 – week course of oral steroid therapy may be considered. Topical or oral antibiotics are used in the case of any secondary infection. Antihistamines may be advised to reduce itch. In chronic allergic contact dermatitis, immunosuppressive agents like ciclosporin, as well as phototherapy, remain possible options. Pennsylvania Dermatology Specialists will adjust the treatment plan appropriately to your needs for the best achievable results.

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