Just want to share an experience I recently had. Having taken the amino acid Arginine for a few days (500mg per day) I developed shingles (or Herpes Zoster). There is absolutely no doubt that arginine was the cause as the virus (which was dormant in my body after having had the chickenpox virus as a child) is known to feed of arginine. Otherwise, I am a healthy 43 yr old male with good immune system. Be warned !