Your son, I am 99% sure that this is true, is abusing the nyquil for the acitve ingredient and intoxicating drug called
DXM, which stands for Dextro-methorphan, used in larger than normal dosages the user feels dissaossociative, has visuals, is light-headed, and has a general "trip" feeling that last for 6 hours to 8 hours. I am 22 and I know in the last five years it's popularity even among the people in my area let alone the whole enitre country has grown emmencially.