Hello, and thank you for your question!
Antihistamines like Aerius and Claritin are effective and safe during pregnancy. Also, I strongly suggest the non-pharmacological strategies below:
Use saline water to irrigate the sinuses, like Hydrasense and Sinus Rinse. These can be used as many times as needed during the day. It's a tad unpleasant but is very effective.
Try not to keep the windows open especially when the allergen index is high, and change your clothing as soon as you come back from an outing. Also, try not to dry your clothes outside during laundry day.
As for biotin, it is present in several multivitamins and is considered safe during breastfeeding. The same can not be said about collagen; there is a lack of information concerning its safety during pregnancy and breastfeeding, ergo I do not suggest taking it while breastfeeding.
Hoping I've been helpful, please do not hesitate if you have other questions.
Tom Samaha, your friendly neighborhood pharmacist