What are the side effects of Acyclovir Topical?
Last updated September 7, 2026.
Most side effects of topical acyclovir are mild and stay in the skin where you apply it, such as dryness, flaking, brief stinging or burning, tingling, and mild itching or redness. Which effects you notice depends on the form: the 5% cream is more likely to dry or flake the skin, while the 5% ointment tends to sting on contact, especially on broken skin or mucous membranes. Very little acyclovir is absorbed through the skin, so body-wide effects like headache or nausea are uncommon with the topical product compared with the pills. Applying a thin layer with a clean fingertip or a glove, letting it dry before covering the area, and washing your hands after each dose keeps irritation and spread down. If the burning is strong enough that you want to skip doses, that is worth a conversation, because the medicine works best when started early and used on schedule. Swelling, hives, or trouble breathing are not typical irritation and need urgent care.
What to do
- Use a thin layer: A thin film that covers the sore is enough; more product adds irritation, not benefit.
- Protect your hands: Apply with a finger cot or glove, or wash your hands before and after, so you do not move the virus to your eyes or other skin.
- Start early: Begin at the first tingle or redness and keep to the full course, since starting late blunts how much the medicine helps.
- Keep it off your eyes: Skin cream and ointment are not made for the eye, the inside of the mouth, or the vagina; eye involvement needs a clinician the same day.
- Soothe dryness: If the skin flakes or feels tight, a plain fragrance-free moisturizer between doses usually settles it.
- Know the stop signs: Hives, facial or lip swelling, trouble breathing, spreading redness, pus, or fever mean you stop and seek care rather than continue.
Related questions
- Are medication side effects worse at first
- Can i get health insurance outside open enrollment
- Can i see what my doctor wrote about me
- Can i text a doctor about medication side effects