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 NICE CKS.
• 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 NICE CKS. Referral is also appropriate if allergy to prescribed or over-the-counter topical treatments is suspected [PCDS, 2022].