Viral challenges can be safe, but there are also the ones that aren't safe like the Tide Pod challenge. The Ice Bucket challenge was good, as it did help raise awareness for ALS I think it was. Viral challenges do have a serious effect on some people, especially the harmful ones, for obvious reasons.
Some trends can enhance social engagement, but it can also cause the peer pressure like you said. Some people will do dangerous things to fit in sometimes. To navigate viral trends like this, make sure you're not doing any of the harmful ones. Do the safe ones, or the ones for charity or creating awareness about something. It's never worth taking up something that could harm you.