How to Stop Reacting Dogs

Anna rates, I have an 18 month old Brittany that has recently been showing signs of developing reactivity. It began about six months ago as occasional mild reactions like a single bar and progressed to more frequent, longer outbursts. She also only reacts when she is with me or my wife, not when she's alone. Her reactions never seem aggressive or fearful, more like she is announcing the presence of the person dog car, etc. If this could be attributed to adolescent big feelings and managed ourselves before it accumulates too much of a reinforcement history, I would like to try.