My wife and I went on a two week vacation, and a day before we left, I began taking 6-12 drops of Sovereign Silver per day, while my wife took another over-the-counter tablet dropped in water to dissolve. We flew on several planes, attended a wedding, visited friends in two hospitals, and traveled to four states in the Northeast. Coming from California, the climate was much different. My wife caught a cold after 4 days. I did not, and I am still taking Sovereign Silver and have never felt better. Thank you.