Food hypersensitivity includes allergies, intolerances and coeliac disease. The numbers affected in the UK are not known for sure, but about 1-2% of adults and 5-8% of children have food allergy, which can lead to life-threatening symptoms. At least one person in 100 has coeliac disease requiring them to avoid cereals containing gluten. Many more report different intolerances to a range of foods with different symptoms. These all require rigorous food avoidance - of ingredients deliberately added to foods, and additional controls to prevent cross contamination of a non-ingredient allergen in the supply chain, preparation or service / sales environment. These individuals and those making food choices on their behalf rely on correct information being provided by all food businesses - via labelling on the packaging, online information, printed menus and folders, or by asking staff. Food businesses also need to assess the risk and put controls in place to reduce allergen contamination and encourage informed dialogue with consumers. In response to high-profile fatalities in the recent years, and after consultation, legislation is changing in October 2021 to require products prepacked for direct sale (made and packed on site for later sale) to carry the name of the food, and the full ingredients list highlighting any of the 14 regulated allergens present. Allergen information for dishes or products made to order must be supplied to customers on request - in writing, or by asking staff, and customers should be made aware that this is possible - on menus and signs on the premises and online. Significant societal changes in the last decade hastened by the global pandemic has led to soaring demand for online food delivery including ready to consume meals, drinks, and snacks; one in four consumers now considers using such services on a regular basis. Food businesses have chosen, or been forced, to adapt accordingly whilst still meeting regulatory requirements to provide information at the point of selection and when the food is collected or delivered. They also need to ensure that their practices and procedures enable consumer requests for allergen avoidance to be recorded and managed, cross contamination controlled, and food prepared specially for such requests to be clearly identified when delivered. Consumers at risk may encounter barriers discussing their particular needs with staff when making such purchases. With the involvement of citizen scientists recruited from the UK public, this project aims to understand the safety, efficiency, practices, and behaviours involved in procuring food online from the perspective of people with food hypersensitivities. Citizen scientists will crowdsource their contributions towards the end goal, working in collaboration with professional scientists, openly discussing and developing their methods. The project duration is 8 months with the work divided into four objectives: 1) recruiting a cohort of motivated citizen scientists following an avoidance diet and recording their perceptions, behaviours and practices 2) mapping procedures and practices of individual food businesses engaged in online food delivery 3) determination by analysis the presence of certain allergens in selected samples procured by participants, using accredited methods 4) effective dissemination of the results in innovative and impactful ways. More specifically, the recruited citizen scientists will not only actively engage in the data collection of the food ordered at their household using their smartphones and computers but also participate in shaping the experimental design and in further stages of the scientific process including the data analysis and result dissemination (co-designed citizen science project). The project's outcomes have the potential to shape future polices in food safety, and its novel methodology will have wider applications for future studies with benefits for all involved.