The Face and the Body is a great day spa on O'Fallon. They offer many services including massages, facials, manicures, pedicures, hair styling and on. You can choose these services individually or there are packages where some of their services are combined.
I highly recommend a Swedish massage. It is a very relaxing hour and a wonderful experience. I received a pedicure there as well. It was nice but if you only have time for one thing, go with the massage!