How fast does acyclovir start working?
Acyclovir’s time to notice improvement depends on the type of infection and how it’s being used (oral tablets vs. topical cream vs. IV). In general, antiviral treatment works by stopping the virus from multiplying, so symptom improvement usually begins after the medication has been taken for at least a day or so, not immediately.
Genital herpes: when should symptoms improve?
For genital herpes, people are typically advised to start acyclovir as soon as symptoms begin (or at the first sign of an outbreak). With timely treatment, pain, burning, and new sore formation often start to improve within about 1–2 days, and healing continues over several more days.
Oral herpes (cold sores): how quickly can you see results?
For cold sores, the practical goal is to start treatment at the earliest tingling/burning stage. When started early, many people notice the sore stops getting worse within about a day, with crusting/healing over the following days.
Chickenpox or shingles: what timeline to expect?
- Shingles (herpes zoster): antivirals work best when started within 72 hours of rash onset. Symptom improvement (especially reduced progression of new lesions and pain) typically takes a few days to become clear, with healing over the next couple of weeks.
- Chickenpox: early treatment can help reduce severity. Improvement generally occurs over several days, with full recovery taking longer.
What if you don’t feel better quickly?
If you’re taking acyclovir but symptoms are not improving after a couple of days (or the rash/sores are rapidly worsening), it’s worth contacting a clinician. Poor response can happen if treatment started late, dosing is off, the diagnosis is different, or the infection is more severe—especially in people who are immunocompromised.
When to get urgent care
Seek urgent medical attention if you have severe illness, fever that’s not settling, eye involvement (pain/redness/vision changes), widespread rash, trouble breathing, or you’re immunocompromised. In these situations, clinicians may adjust treatment urgently or switch to another approach.
Does “works” mean different things for different symptoms?
Yes. Acyclovir often reduces new lesion formation first, while pain and healing take longer. Some people feel pain relief sooner; others notice improvement mostly in how quickly new sores appear and how fast existing ones crust over.
Sources
No sources were provided with your question, so I did not cite any external references. If you tell me whether you mean oral acyclovir tablets, topical acyclovir cream, or IV treatment—and whether this is for cold sores, genital herpes, shingles, or chickenpox—I can give a more precise timeline for that specific use case.