How can I differentiate between allergic and irritant contact dermatitis in a primary care setting?

Differentiating between allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) in a primary care setting can be challenging, as their clinical features alone are often unreliable [BAD, 2017; White, 2016]. Expert opinion indicates that it is frequently difficult to distinguish between the two clinically [White, 2016].

• Clinical Features: While both can present with similar symptoms, clinical features alone are not reliable for differentiation, particularly in chronic or persistent cases, such as hand and facial dermatitis [BAD, 2017].
• Patch Testing: The definitive method for identifying specific allergens in suspected allergic contact dermatitis is patch testing [Fonacier, 2018]. The British Association of Dermatology recommends offering patch testing for individuals with chronic or persistent dermatitis, especially when clinical features are unreliable in distinguishing between allergic, irritant, and endogenous dermatitis [BAD, 2017]. Identifying the specific allergen through patch testing can improve adherence to avoidance and overall outcomes [Fonacier, 2018].
• Management Considerations: Due to the difficulty in clinical distinction, topical corticosteroids are often recommended for symptomatic treatment where irritant contact dermatitis is suspected, similar to their use in allergic contact dermatitis [Rashid, 2016; White, 2016; Dickel, 2022]. Avoidance of the causative stimulus is the most crucial step in treatment and prevention for both types of contact dermatitis ¹.
• Referral to Dermatology: Referral to dermatology should be considered if the contact dermatitis is severe, chronic, recurrent, or persistent, or if the diagnosis remains unclear despite primary care management ¹. Referral is also appropriate if allergy to prescribed or over-the-counter topical treatments is suspected [PCDS, 2022].