What investigations should I consider for a patient with suspected contact dermatitis who is not responding to initial treatment?

For a patient with suspected contact dermatitis not responding to initial treatment, the primary investigation to consider is referral to dermatology NICE CKS.

• This referral is appropriate if the suspected contact dermatitis does not respond to treatment in primary care, has atypical features, or if the diagnosis is unclear NICE CKS.
• Once referred, patch testing should be offered, particularly for chronic or persistent dermatitis, especially on the hands and face, as clinical features alone are unreliable in differentiating between allergic, irritant, and endogenous dermatitis NICE CKS BAD 2017.
• Referral to dermatology is also recommended if an allergy to prescribed or over-the-counter topical treatments, such as neomycin or corticosteroids, is suspected NICE CKS PCDS 2022.
• Identifying the specific allergen through patch testing can increase patient adherence to avoidance measures and improve treatment outcomes NICE CKS Fonacier 2018.