Lip Dose Challenges in Food Allergy: Current Practice and Diagnostic Utility in the United Kingdom

Lip dose challenges (LDCs) are often performed as an initial step before oral food challenges (OFCs). However, guidance on how to perform and interpret LDCs is unclear, and data are lacking regarding the diagnostic accuracy of LDCs.

To investigate current practice with respect to LDCs among UK allergy health care professionals, and to evaluate the diagnostic utility of LDCs in children undergoing OFCs for IgE-mediated food allergy.

We used an electronic survey to assess the use of LDCs by UK Allergy clinics. Separately, we prospectively recruited children undergoing "low-risk" OFCs for suspected IgE-mediated food allergy from 2 large specialist allergy units in London. LDC was performed 30 minutes before the OFC, by applying the food to the inner lip for 30 seconds. Objective symptoms were considered a positive outcome. All patients subsequently proceeded to OFC regardless of LDC outcome, and outcome assessed according to PRACTALL consensus.

We received 147 responses to the online survey, representing 67% of registered pediatric allergy clinics in the United Kingdom. Eighty percent of respondents (representing 81% of responding centers) included LDC as the first step of OFC in routine clinical practice. There was a wide variation in both how LDCs were performed and interpreted, with one-third not proceeding to OFC if LDC resulted in subjective symptoms. In the prospective study, 198 children (mean age, 7 years) with conclusive OFCs were included. Foods tested were tree nuts (30%), peanut (16.6%), egg (16%), fish (10.5%), milk (6%), shrimp (4%), and other (16.9%). There were 12 positive LDCs (1 of which triggered systemic symptoms: generalized urticaria) and 31 positive OFCs. Two children with positive LDCs went on to have a negative diagnostic OFC. Sensitivity of LDC was 32%, specificity 98%, with a false-negative rate of 68%.

Most UK allergy clinics included LDC as an initial step during OFC, despite a wide variation in how LDCs are performed and interpreted, which raises major concerns about the reproducibility and the validity of the test. We found that LDC had poor sensitivity as an alternative or initial step to formal OFC.