What does Listerine do.

[PaphMadMan]

Both Listerine and hydrogen peroxide can be effective on external bacterial infections - much less effective against non-bacterial pathogens or systemic (internal) infections. Listerine will have a much longer residual effect than hydrogen peroxide, if you're looking for something that can prevent infection. Neither will cause any harm on healthy external tissue except on very delicate plants. On a freshly cut surface hydrogen peroxide can penetrate pretty deeply through the plants vascular system and cause damage. Listerine is less likely to do so.