Allergic Contact Dermatitis 

Definition: Allergic contact dermatitis (ACD) is a skin condition that occurs when the skin comes into contact with an allergen, leading to an immune response and subsequent inflammation(1).

Etiology: ACD is caused by an allergic reaction to substances that come into direct contact with the skin. Common allergens include nickel, fragrances, preservatives, latex, and certain plants like poison ivy (1,3). The immune system recognizes these substances as harmful, triggering an inflammatory response(1).

Epidemiology: ACD affects individuals of all ages, but it is more prevalent in adults due to cumulative exposure to allergens over time. It is common with some studies demonstrating a prevalence rate of 20% in the general population (2). It is particularly common in certain occupations that involve frequent contact with irritants and allergens, such as healthcare workers, hairdressers, and construction workers (2). 

Signs: Key signs of ACD include erythema, edema, vesicles, and lichenification in chronic cases (1). These signs typically appear in areas directly exposed to the allergen(1,2).

Symptoms: Symptoms of ACD include intense itching, burning, and discomfort at the site of contact(3). The skin may also become dry, cracked, and scaly if exposure continues or if the dermatitis becomes chronic(3)

Differentials: Differential diagnoses for ACD include irritant contact dermatitis, atopic dermatitis, psoriasis, fungal infections, and seborrheic dermatitis (1).

Diagnosis: Diagnosis of ACD is primarily clinical, based on the history of exposure and characteristic skin findings(1). Patch testing is the gold standard and is used to identify the allergens that cause allergic contact dermatitis (1).

Treatment: The cornerstone of ACD treatment is identifying and avoiding the offending allergen(1). Topical corticosteroids are commonly prescribed to reduce inflammation and alleviate symptoms(1). In severe cases, systemic corticosteroids may be required. Avoidance necessitates thorough label-checking for the allergen and related cross-reactive substances. Understanding these cross-reactive ingredients and knowing where a particular allergen is commonly found can aid in effectively advising the patient (1).

References: (AMA)

1. Kanwaljit K. Brar MD, AbstractObjectiveTo familiarize the reader with the mechanisms and causes of contact dermatitis.Data SourcesRecent research articles, Dhingra N, et al. A review of contact dermatitis. Annals of Allergy, Asthma & Immunology. October 20, 2020. Accessed August 10, 2024. https://www.sciencedirect.com/science/article/pii/S1081120620310802.
2. Stacy Nassau MD, Jacob SE, Warshaw EM, et al. Allergic contact dermatitis. Medical Clinics of North America. October 28, 2019. Accessed August 10, 2024. https://www.sciencedirect.com/science/article/pii/S0025712519300884. 
3. Brandon L. Adler M. Allergic contact dermatitis. JAMA Dermatology. March 1, 2021. Accessed August 10, 2024. https://jamanetwork.com/journals/jamadermatology/article-abstract/2775575.