I was given Singulair after a serious bout with asthma several mo...

I was given Singulair after a serious bout with asthma several months ago. I only took a few because every time I took them, it seemed I got a terrible headache. I was out of Allegra today and needed to take something for my allergies so I could go to work, so I took a Singulair.My allergies were good all day until I started getting hives. Huge hives the size of a quarter. Since I knew I didn't eat anything different, I came on here to see if that was a side effect and sure enough, it is.