In my old age I have developed seasonal allergies. I received a prescription to help alleviate the symptoms. First, I checked with my FAA examiner about using it when I fly and he said it was not on the list of medications that ground you.
Secondly, anyone can check AOPA's tool that gives you that answer anonymously http://www.aopa.org/members/databases/medical/search_faa_meds.cfm?action=search.
The medications I use do not restrict me from flying but as you can see from the below FAR, that doesn't mean I should go flying. The medical condition could be as simple as "I don't feel well" you need to feel 100% percent before you go flying. These FARs are for your safety, do you feel your best today as you preflight? If not, then rescheduling may be an option for you. Taking off is not mandatory!
§ 61.53 Prohibition on operations during medical deficiency.
(a) Operations that require a medical certificate. Except as provided for in paragraph (b) of this section, a person who holds a current medical certificate issued under part 67 of this chapter shall not act as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person:
(1) Knows or has reason to know of any medical condition that would make the person unable to meet the requirements for the medical certificate necessary for the pilot operation; or
(2) Is taking medication or receiving other treatment for a medical condition that results in the person being unable to meet the requirements for the medical certificate necessary for the pilot operation.
(b) Operations that do not require a medical certificate. For operations provided for in §61.23(b) of this part, a person shall not act as pilot in command, or in any other capacity as a required pilot flight crewmember, while that person knows or has reason to know of any medical condition that would make the person unable to operate the aircraft in a safe manner.
(c) Operations requiring a medical certificate or a U.S. driver's license. For operations provided for in §61.23(c), a person must meet the provisions of—
(1) Paragraph (a) of this section if that person holds a valid medical certificate issued under part 67 of this chapter and does not hold a current and valid U.S. driver's license.
(2) Paragraph (b) of this section if that person holds a current and valid U.S. driver's license.
