Can i take alavert d and tamiflu (oseltamivir) together?

Yes: Alavert d is for allergies. Tamiflu (oseltamivir) is to decrease the symptoms and length of time you have a flu. You can take them together, but you usually don't need to since tamiflu (oseltamivir) is only useful if you do have the flu and it is very early in the course and your symptoms are likely from the flu instead of allergies. If you have allergies, it is useless to use tamiflu (oseltamivir).