Frothers, as you call them, are surfactants. They have a polar end and a non-polar end - usually they are a long molecule. This makes them very active if they are in the interface of air and water - like on the walls of bubbles.

Water molecules are attracted to each other and in the surface of water their attraction is quite strong, this is a high surface tension, almost like skin. But when a surfactant molecule enters the surface, it breaks up the water structure, and the surface tension of the solution decreases.

Quick experiment. On a table that you can make wet, or on a sheet of plastic, put some water and spread it around to make the surface wet. take a drop of soap on your palm, mix it with water, and touch a soap wetted finger to the center of the water area. You will see that the area of the soap becomes almost dry - it is a region of low surface tension and the pure water around it has a much higher surface tension and the water pulls away. As you can see it is a very strong reaction. You can also do this with a drop of rubbing alcohol. This effect, the water pulling away, is called the Marangoni effect.

If you see someone drinking a wine or liquor, you will see drops running down the inside walls of the glass. You'd have to wonder where they come from. This is the Marangoni effect - alcohol lowers surface tension, but near the top of the glass edge, alcohol is also evaporating rapidly, increasing the surface tension near the edge of the glass. Just like on the table experiment above, the high surface tension literally pumps liquid up the walls of the glass, it becomes too heavy and rolls back down.