You can use your HSA and FSA tax-preferred savings account to purchase OTC products including Flonase. The passage of the CARES Act by Congress includes provisions to restore OTC eligibility under tax-preferred HSA and FSA accounts. Your plan details may vary, so save your receipt and check with your benefits or health provider for eligibility.
Source: https://www.chpa.org/Monograph_FSA_CARES.aspx