If your son treat that as healing flu, he'll not fight it. He'll heal in a week or two. I've got this a few times, once in 2020 and twice in 2021. I didn't make any test. I understand that's it because I couldn't smell anything. So, I treated that like a flu and I'm ok now.

I just breath more fresh air, open windows, go out often, drink a lot of water, eat lemon and honey. Eat healthy, no alcohol, no smoking. Sleep weel and that's always helping and that can help anyone. When doctors start to give antiboitics and special drugs for covid, the situation bacame just worse. If everyone treat that as a flu, everyone will be ok.