@hschaap Hills, Purina, and Royal Canin are all great brands with extensive science behind them. Purina Pro Plan has a sensitive skin & stomach formula that comes in salmon, turkey, or lamb.
@oceania The royal canin ultamino is supposed to be one of the most hypoallergenic diets. I just checked and it does not contain oats or peas. you would need to ask your vet about it, it’s a prescription diet.
@confused1980 Most allergies are environmental. A food trial with an hydrolyzed protein diet is the best way to diagnose a food allergy. A quick search on Chewy I found a few of the Acana singles line meet your requirements and the Natures Logic pork seems to as well.