Antihistamines are found in many over the counter allergy and cold medicines. A product with an antihistamine and a nasal decongestant should help to relieve the symptoms associated with the allergic reaction. Prescription allergy medications may be necessary for those with higher sensitivities to the allergens. It may be necessary to take antibiotics to get rid of any infection.
Over the counter relief can be found in decongestants (reduce swelling in nose) or antihistamines. The doctor can provide prescriptions for sprays or stronger meds. Also keep dogs off of the bed where you sleep, as well as filter the air and clean well.
You can give your dog some Benadryl. As a rule, you can give 1 to 2 mg of children's Benadryl for each pound your dog weighs (i.e. if you have a 3 lb dog, you may give it between 3 and 6 mg).
There are several anit-allergy medications that are available without a precription from your local pharmacy or grocery store. If the problem persists, you can see a doctor and he may be able to prescribe something stronger to help with your clogged sinus.
Having a similar situation with cats, I typically use over the counter decongestants tablets, and saline nasal spray. Saline spray is basically sterile salt water used to hydrate the mucus membranes inside the nose.