I've read them too. On Facebook groups, Reddit forums, and had members of our monthly Support Group ask questions about it. 

The women sharing they're PMDD free because of Zyrtec. I wish it worked for every one of us, but from what I am hearing from clients and online chat forums is that it takes the edge off for some, and doesn't make a difference for others. 

At present, there are no peer‑reviewed clinical studies or controlled trials showing that H1 or H2 blockers like Zyrtec, Claritin, Pepcid, or famotidine treat PMDD mood symptoms. Searches of the literature fail to find trials linking antihistamine use with symptom improvement in diagnosed PMDD populations. In other words: there’s literally no scientific evidence that antihistamines treat the underlying biology of PMDD.

Because PMDD is not a hormonal imbalance. Your estrogen and progesterone levels are normal — the problem is how your brain responds to these natural changes. That’s why some women notice relief from H1 or H2 blockers (like Zyrtec or Pepcid) during the luteal phase. GABA‑A receptors in the brain normally respond to allopregnanolone, a progesterone metabolite that calms the nervous system. In PMDD, these receptors are overly sensitive or misfiring, which can trigger anxiety, irritability, and mood swings. 

Histamine may play a role too — estrogen can trigger mast cells to release more histamine, and some women report their luteal‑phase symptoms improve when taking antihistamines. But there’s no clinical research proving H1 or H2 blockers treat PMDD. What we do know is that anecdotes matter, especially in women’s health where research is limited. 

Honestly, a pack of Zyrtec is cheaper and gentler than vodka, whilst there's no evidence that it works there are hundreds of women sharing that it took the edge off their symptoms. I’ve got my own theories about Mast Cell Activation Syndrome being a sub‑type of PMDD along with progesterone sensitivity (why birth control works for some but not for others) — but again, we’re back to anecdotal evidence. If it works, it could be a lovely addition to your toolbox - but it shouldn't be the only thing. You can also add the PMDD Reset Method with support groups, community, and evidence-based strategies to help you navigate your cycle.