Does a sinus rinse out your sinuses in your forehead ?

Not really: The sinus rinses mainly just rinse out the nasal cavity. The paranasal sinuses (including the “frontal sinus” in your forehead) connect with the nasal cavity, however, little, if any, of the rinse is likely to get into your sinuses. The nasal cavity (behind your nose) is where you'd catch dust and pollen as you breath in through your nose. So, it is a good place to rinse out.

Frontal Sinus Rinse: Greetings. Saline nasal irrigation used in a normal nasal cavity without having had surgery will not enter the frontal sinus proper. The reason for saline irrigation is clean the nasal mucus membranes returning them to normal health. In doing so, the rest of the sinuses will improve as well. The lining inside the nose connect to the sinuses and the ear. I hope this helps.