Can i still take acyclovir 200 mg 1 wk after 1st chickenpox rash appeared. doc says taking acyclovir at this stage will make me less infectious.

Is diagnosis correct: At age 27 this infection is usually serious. If diagnosis is correct you should have started 1 week ago at 800 mg 5x a day for a week. Valacyclovir 1000mg 3x a day is more effective. Yes, it will make you less contageous.

Yes you can: This is the only prophylaxis that exist. A vaccine to prevent hz is now available and strongly suggested for individuals over 60, your age is 27 and that's ok too.

I don't accept it: You are contagious for 7 days from the first spot or until the last spot dries, whichever is latest. I would never rely on such a low dose of acyclovir to eliminate your potential to pass the germ. If your spots have dried out, you don't need anything to resume your public activities.