Hi. I'm Dr. Lee and will do my best to help.
How much does your dog weight?
Any discharge from the nose? If so, what color?
Thanks for the update.
I would suggest to get some human over the counter Chlortrimetron 4mg tablets and give 1/2 tablet every 12 hours to help with the nasal congestion. This drug is an anti-histamine that also can help dry up the nose. If after giving this for 2 to 3 days and there is no improvement, then she needs to go back to your vet for a recheck and get some prescription medication.
Please let me know if you have any questions or concerns. Thanks.
Benadryl is only antihistamine with no effects for the nose. Chlortrimetron is the one to use for nasal allergy problems.