I get headaches daily and i wondered if allergies can cause them, mri's and sinus catscan showed nothing, i have allergies and i take claritin during the day and benadryl at night, i seem to feel better after taking them, is that why im getting them?

Sounds like a reasonable hypothesis to me. Discuss with your Dr who knows allergies where you live.

Allergic reactions could trigger headaches, but unlikely to be the root cause. Allergies are very often associated with migraine. Your headaches could be due to tension cephalgia, jaw, sinus, neck, dental, and even inflammatory causes. Your doctor should be able to sort all of these out.