Plasma (aka Blood Meal) is a high-protein ingredient derived from pig or cow blood. This isn't necessarily a bad ingredient - it just doesn't sound too appealing. It is a high protein, low ash, low fat ingredient used to help balance out a formula's protein and calcium levels - especially when using ingredients like Beef & Bone Meal.  Our only issue is this ingredient is anonymous. It could be derived from a variety of species and a mixture of several animals. It would be very difficult to isolate a food allergy or intolerance with an ingredient like blood meal or plasma present while your pet is being evaluated using an elimination diet. We prefer to know the source species.