Remove the loess smooth standard error gray area (or apply alpha to it)

The following code returns the plot below.Is there a way to remove the standard error gray area or apply alpha to it so it's not so saturated? Especially the case where many lines are plotted this can interfere in the visualization. Thanks!

library(GGally)library(ggplot2)ggpairs(swiss[1:3],         lower=list(continuous=wrap("smooth", colour="blue")),        diag=list(continuous=wrap("barDiag", fill="blue")))