Here's some sources on it.
Singulair Fucks You Up: https://www.usatoday.com/story/news/health/2024/11/24/singulair-asthma-study-mental-health-fda/76549193007/
Most of the studies for Xyzal say its safer than previous antihistamines... but fuck that noise.
Long and short... if you're using seasonal meds and you don't have brain issues. Great.
If you are suffering from brain issues and you ARE taking seasonal allergy meds - whatever kind. Try not taking them for a month and see if you notice a difference.