Anti-histamin

[Gambitdbn]

The earlier antihistamines had quite a few spillover effects resulting in side effects like the tachycardia and drowsiness (leading to some being marketed as sleeping tablets). As was said before this has largely being eliminated (although not entirely) in later generation drugs, but they still carry a risk of increasing your predisposition to cardiac arrhythmia - especially during exercise.

That said, if you don't have any underlying cardiac problems the risk is probably not too significant.

 

Personally I wouldn't take any OTC meds before exercising unless I had to. Also be sure that your runny nose is an allergy and not a mild viral infection. If you feel at all a bit feverish or unwell, rather just stay at home...