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What is allergic contact dermatitis (ACD)?

 

Dermatitis, also known as eczema, is a broad term used for certain types of skin rashes. Irritant dermatitis, atopic dermatitis and allergic contact dermatitis (ACD) are a few common diagnoses for people with eczema. 

 

Allergic contact dermatitis (ACD) is a type of dermatitis triggered by an allergen that has come in contact with the skin. An allergen is a substance that has been identified by your body as a foreign invader. Some substances can become an allergen after one exposure, and some will take months or years of repeated exposure before your body identifies it as an invader. Once deemed an invader, the body produces an immune response to protect itself which is a process known as sensitization. Once an individual is sensitized to a specific allergen, skin reactions will occur and worsen after repeated or prolonged exposure to the allergen. 

 

Allergic contact dermatitis (ACD) is a type IV hypersensitivity, the reactions are delayed and mediated by T cells. It takes the body, on average, 48-72 hours to develop a rash after an exposure. Correctly identifying allergens through patch testing and strict avoidance is necessary to heal this type of dermatitis. If strict avoidance of allergens is followed and eczema persist, systemic contact dermatitis (SCD) may be suspected. 

 

Systemic contact dermatitis (SCD) is characterized by developing symptoms, most commonly skin rashes, from exposures to an allergen by various routes, not limited to physical contact. Ingesting, infusing, inhaling and implanting are other ways in which we are exposed to allergens. Individuals with SCD will experience symptoms, such as a relapse in eczema, when exposed to allergens via any route. For example, if a person with a nickel allergy has SCD, they could experience a flare in rashes 1-4 days after eating foods high in nickel, such as chocolate, nuts, seeds, beans, soy, and whole grains. 

Symptoms of ACD

• Red rash • Itching • Bumps • Fluid-filled blisters • Swelling • Warm to touch • Cracks • Dryness • Tenderness

 

Common contact allergens

 

• Nickel​ • Cobalt​ • Fragrance • Chromium • Balsam of Peru • Isothiazolinones • Neomycin • Bacitracin
• Phenylenediamine • Formaldehyde • Lanolin • Propylene Glycol • Corticosteroids


Diagnosis

 

Patch testing is the gold standard for diagnosing allergic contact dermatitis (ACD). It is a noninvasive diagnostic test where substances that contain common allergens are placed on a large area of the body, most commonly the back. Once test substances are applied, they are secured with hypoallergenic tape and left on the body for 48 hours. After an additional 48 hours, results are read. Most dermatologists will place patches on a Monday, remove patches on Wednesday and read the final results on Friday. Delayed reactions may occur, request your dermatologist label patch test sites so any delayed reactions can be noted.  

 

Treatment 

 

There is no cure for ACD. Strict avoidance is necessary to heal rashes. Some other treatment options include:

• Phototherapy • Diluted vinegar/bleach baths • Topical steroids • Barrier creams or techniques (wearing gloves)
 


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