How quickly does acyclovir start working?
Acyclovir (including oral acyclovir tablets and other forms like topical acyclovir) typically begins reducing viral activity soon after you take it, but the visible benefit usually takes longer. For many people, improvement is noticed within about 1 to 2 days, with clearer healing over several days.
How long until symptoms get better?
The speed of symptom relief depends on how and when you start:
- Starting early (within about 24 hours of symptoms, or when a rash/lesions first appear) usually works best and can shorten the course.
- If you start later, it may still help, but symptoms often take longer to improve.
For typical herpes outbreaks, lesions often begin drying and healing within a few days, and most people see substantial improvement over roughly a week.
What’s different between cold sores, genital herpes, and shingles?
Acyclovir dosing schedules differ by condition, and that affects “time to effect”:
- Cold sores (herpes labialis): improvement often shows up within a day or two; healing commonly takes several days.
- Genital herpes (herpes simplex): pain/tingling may improve within 1 to 2 days once treatment is started, with healing over days to about a week.
- Shingles (herpes zoster): it works best when started early; earlier treatment can reduce the duration and severity. Pain improvement may take longer than rash changes.
Does acyclovir prevent new lesions?
Yes. When started promptly, acyclovir can slow viral replication, which usually means fewer new lesions form and existing lesions heal faster than they would without treatment. If new spots keep appearing after you’ve been on it for a day or two, it may mean treatment was started late, the dose/frequency isn’t optimal, or the situation needs medical review.
When should you contact a clinician urgently?
Seek medical help right away if any of these apply:
- You have a weakened immune system.
- Eye involvement (eye pain, redness, light sensitivity, or vision changes).
- Severe symptoms, fever, or rapidly worsening pain.
- No improvement after several days of treatment, or lesions that are spreading despite therapy.
Important practical note
If you tell me which form you’re using (oral vs topical), and what condition it’s for (cold sore, genital herpes, shingles, or something else), I can give a tighter estimate for “how long until you feel it working.”