Language barriers hamper or delay delivery of urgent and emergency care to migrant children when they or their parents don't speak any of the languages commonly spoken in Switzerland. In such situations, nurses often fall back to use ad hoc communication aids, including translation apps and visual dictionaries, to collect information about a patient's medical history. In this paper, we report on the participatory design process for a novel image-based communication aid. It is specifically tailored to the needs of migrant patients and nurses within Swiss pediatric clinics. We collected requirements in surveys and in-depth interviews with pediatric nurses. A prototype app was developed and tested with users in a scenario-based usability test. The results clearly show that the images developed, especially for symptoms, accidents or nutrition and excretion, are well comprehensible for triage and anamnesis. In contrast, a temporal classification or chronological occurrence of health incidents is difficulty to express with images.