Your dog’s immune system springs into action every time his body recognizes something that threatens his health. If his immune system is strong, the defending cells fight back and counteract any potential infection being carried by parasites, bacteria, virus or fungi, before any symptoms manifest. If his immune system is weak, infections and illness occur. To strengthen your dog’s immune system naturally, you must establish a diet consisting of natural foods and other elements. Providing this type of diet to your dog boosts his immune system and improves his health overall.