Hey, Nancy...Oban could have a sensitivity to the food that your animal protein source is eating at different times of the year (e.g., grass-fed vs. hay-fed). That doesn't make identifying food as the source any easier but it can explain the issue. This also applies to why some batches of nuts or whatever might not give a problem but others will...cross-pollenization and also water source for seasonal watering and what's in the soil in different places. It's enough to make you crazy if you're sensitive to a lot of things.