How long after taking doxycycline do i have to stay out of the sun?

Doxycycline sun rash: Doxycycline absorbs UV-A, so if you're outdoors when the med is in your system, you could wind up with a photosensitive rash. That rash can be nasty -so it's good to be careful. The half-life of the drug is about 20 hrs, and it binds to proteins in the body. Thus, after about 5 half-lives since you last took the drug, 'all of it' should be out of your system. That's 4-5 days as the other docs said