What is the best mouthwash to use when all your gums are swollen. i don't have a infection and i have a tooth coming tough?

Simplest is best: Simple salt and water is the best in this circumstance. A level teaspoon in a drinking glass of warm water should work. You should see your dentist as well.

Swelling: At 26 you're a little old for normal tooth eruption. Best to have your Dentist take a look. Salt water rinses (1tsp in 8oz water) may sooth the area, but it really should be checked to make sure there is no pathology.