Lowercase columns names of dataframes inside list

I have multiple csv, so I've used glob and read_csv, append each one inside a list then did concatenated all of them.

My question is how can I access to the columns names and lowercase them ?

EDIT:

    allfiles = glob.glob("*.csv", )
    dataframes = []
    for file in allfiles :
        dataframes.append(pd.read_csv(file, sep=";", decimal=","))
    df = pd.concat(dataframes)

Thanks !