Is it safe to proceed with a Restylane top off for my tear troughs or should I wait until my allergies have subsided?

To ensure you receive optimal results it is
recommended to wait until your allergies have subsided. If at all possible,
taking Claritin, Allegra, or even Patanol then waiting about a month will help
resolve any allergies. It is pertinent to take care of any allergy issues prior
to injections so that it does not affect the results or outcome. 

If you are suffering from seasonal allergies it can definitely affect how "swollen" you appear in the under eye area.  I would wait until the allergies are controlled before I had this sensitive area injected.

FSRB, I know of no contraindications to injectables and seasonal allergies. By the way, try eating local honey; good evidence it helps airborn local allergies.