Here's what you'd need to look for at a Japanese pharmacy if you run out & the last two are probably handy docs to keep cached in Google Doc if needed, anyhow
Finding Allergy medicines in Tokyo | unclassified
https://blog.gaijinpot.com/allergies-in-japan/
User blog
emonaCarrolltucky/Nose Sprays | Tokyo JET Wikia | FANDOM powered by Wikia
https://www.reddit.com/r/japanlife/wiki/medical - Primary Care OTC Medication handbook
http://www.kaigai-iyaku.com/drugs-name-list.pdf
Why not just bring a small box of Zyrtec & Allegra generics in blister packs? It would mostly be the pseudoephedrine (or -D versions) which you need to avoid importing. You can bring up to one month's worth for personal use without Yakkan Shoumei
Ministry of Health, Labour and Welfare: Information for those who are bringing medicines for personal use into Japan
Japan also has some medications with Pseudoephedrine < 10% of overall composition for those who need it as a nasal decongestant (myself included). It seems to be in some of the rhinitis medications like Pabron S, Benza Block L, Precol L/LX
https://www.reddit.com/r/japan/comme...dafed_allergy/
Ingredients - please click through as needed & google translate as some are meant as cold medicines and all seem to include some caffeine which I don't believe the US generics do. 120 mg/pill seems to be standard size.
Precol L/LX (L = 120 mg Pseudoephedrine hydrochloride + 100 mg Caffeine, LX - + 10 mg Phenylephrine hydrochloride )
https://www.daiichisankyo-hc.co.jp/p...ecol_bien_cap/
https://www.daiichisankyo-hc.co.jp/p...l_bien_cap_lx/
Benza Block L (135 mg Pseudoephedrine hydrochloride + 75 mg Caffeine + 450 mg Ibuprofen)
BENZA BLOCK L | Takeda Pharmaceutical Company, Ltd.
Pabron S capsules ( 60 mg Pseudoephedrine hydrochloride + 50 mg Caffeine)
- Strengthening the Pabron Rhinitis series - Release of "Pabron Rhinitis Capsule-S" and "Pabron Rhinitis Capsule-S for Children" | Taisho Pharmaceutical Co., Ltd.
https://www.catalog-taisho.com/04579.php