Is it bad to continue taking a pill even after getting an allergic reaction?

Sometimes messing around with hormones can cause hives, i mean the ones in your body. But this sounds like it could be the meds or birth control hormones. You need to consult your doctor and ask this, because no one can really answer that like they could.

If I were in your place, i would discontinue the use of those pills, and hope to find one that didn't cause a reaction of ANY kind.

Itching with codeine (or any other opiate) is NOT allergic - it is a normal and very common side effect. If you get hives, or have trouble breathing, THAT is an allergy. (Pruritis occurs with activation of mu opiate receptors; allergic reactions are due to an immunologic reaction) It might be worthwhile to try another painkiller if the itching isn't relieved with Benadryl.

There are so many types of birth control. You need to keep switching until you find the right one. I had the same problem and finally found one.

You should find an alternative pill. Tell the doctor so you can work on finding something that works without the allergies.

Good luck!