No cold for 2.5 years (or more) ... but why?

I've generally been healthy for most of my life, but I used to get a cold maybe once a year:

For some reason, though, I seem to be in a period where I'm not getting any respiratory infections.

I did start getting flu shots regularly in 1997, and I haven't had the flu since. This one is obviously beneficial.

But a couple of changes I've made the last 3-4 years make me wonder:

• I started taking a boatload of magnesium and potassium to control afib, which I found out I had about 18 months ago
• I stopped using almost all shampoo and soap, except on the palms of my hands, in 2014
• I changed to a low-carb diet in 2015 ... 

Maybe one or some combination of these did the trick ... an improvingly healthy gut biome plus plenty of essential minerals. Could be, I guess.

Whatever the reason(s), I'm very grateful!