What are the side effects of Acyclovir Buccal?
Last updated September 7, 2026.
**Acyclovir buccal can cause headache, gum pain or irritation, and canker sores.** You use this cold sore medicine as a tablet that sticks to your upper gum and dissolves slowly. Most treatment related side effects in studies were mild or moderate. Your allergy history matters because the tablet contains milk protein. Let it dissolve without chewing or sucking it, and contact your clinician if mouth discomfort is severe or does not go away.
What to do
- **Check allergies:** Tell your prescriber about any allergy to acyclovir, valacyclovir, or milk protein before using the tablet.
- **Let it dissolve:** Keep the tablet on your upper gum without chewing, crushing, or sucking it.
- **Avoid disturbing it:** Avoid chewing gum and touching the tablet while it is attached.
- **Report ongoing symptoms:** Contact your clinician if gum pain, irritation, or canker sores are severe or do not go away.
- **Get emergency help:** Call 911 if you have trouble breathing or swelling of your tongue or throat.
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