Traveling through Brussels, my saline solution, which is legal for US TSA, was declared illegal.
Are medical exclusions different for USA Travel and Foreign travel?
Just so we are clear. Security at airport(s) in Brussels is not the responsibility of the US TSA even if flight is coming from or going to the US.
If you're interested you can go to the Brussels Airport Site on Bags & Security for more details on what is and is not allowed on board which among other restrictions states:
Saline Solution isn't a dietary supplement nor it is a medicine so if you require it on board you should probably have a doctor write a letter authenticating that you require to have Saline with you at all times for a medical reason.
There are exception to the Liquid and Gels Policy but Saline still doesn't qualify. So if you brought a large bottle of it with you on board the security personnel seem to be well within their right to disallow it.
No, the rules are not different.
Currently the rules for liquids are exactly the same in US and EU.
The rules are:
Also in both in US and EU exceptions apply, but they are especially the same:
The rest is up to security screening officer, his interpretation of the rule and your ability to convince him that liquid is „medically required”. I imagine that outcome would vary even with different TSA agents at same airport. You just got lucky once.