Information Reviews Ask Dr. Dan Product Description Perque L-Histidine Guard supports digestion, immune health, cognitive function, joint health, and muscle strength and recovery. Recommended Use: Take 1 capsule 30 minutes before meals, or as directed by a healthcare professional. Label Information Perque L-Histidine Guard Facts: 1 capsule contains: L-Histidine 650 mg Vegetable capsule (Plantcaps) 120 mg Medium chain triglycerides (MCT) 8.5 mg Maltodextrin (Tapioca) 8.5 mg Other Ingredients: none.