The complexity of the mast cell is becoming more prominent. From being the cell recognized just to contribute to allergic inflammation it is now also associated with wound healing, protection against tumor growth and in recognition and defense against a wide range of pathogens. The location of the mast cell in the barrier between the external and internal environment of the body enables the cell to quickly respond to invading bacteria, virus and parasites. Diarrhea due to Escherichia coli infection, listeriosis, toxoplasmosis, Newcastle disease and bovine respiratory syncytial virus are examples of mast cell activating diseases that can affect animals in, as well as outside, the agricultural sector. Additionally, ticks and tick-borne diseases are of concern.