I eat a healthy diet and take magnesium, zinc, K2, D3 each day. I also take Hydroxychloroquine every other day (for IBS).
I developed a slight sore throat and started to sneeze. My nose started to become blocked. I inhaled 0.1% hydrogen peroxide solution using an ultrasonic nebuliser several times during the evening and night. The following morning the symptoms had almost disappeared and by afternoon I was fine.
I make the 0.1% solution by mixing 1 ml of 3% Hydrogen Peroxide (from any pharmacy) with 29 ml of deionised water. It has a faint smell when inhaled but doesn't sting or cause me to cough.
DISCLAIMER: I'm not a doctor; I'm not telling anyone to try this.
I occasionally nebulize a 1.5% hydrogen peroxide solution. 50/50 3% with diy Himalayan salt saline. I do this as a mostly but not always former heavy smoker.
Or maybe its a 1%, I don't remember but I'd played around with a couple different ratios.
I find it helps break/loosen phlegm up for coughing out.
I wouldn't recommend this whatsoever if you have good healthy lungs. Not that it burned or caused any discomfort, its well above the strength I've seen of any hydrogen peroxide nebulizer solution I've seen.