I've only been on Doxycycline Hyclate for 2 weeks - I am supposed to take it for 2 months to clear up my acne. The first side effect I experienced was the nausea/vomiting. I HAVE to eat something before I take it or it makes me throw up. I was sensitive to the sun, but the thing that was the most bothersome was the tingling in my feet & hands. When water touched them, they would tingle as if they were asleep. It was a very weird feeling. The worst side effect for me, though, are my mood swings. I get so angry I feel almost like I'm going to explode. I can't just drop it like I usually do - I just keep fighting & yelling - which is not like me. I've been saying things I don't mean & lashing out over stupid small things. I feel almost as if I'm going crazy. This is just the first 2 weeks, after reading this board, I'm wondering if it's even worth continuing. Supposedly, when this is prescribed for acne, most cases come back after you stop taking the pill. If it's going to come back anyways, I'd rather not put myself through this for 2 months...