It's often been said that in the early part of the nineteenth century you would have been well advised to stand up wind of anyone with whom you were having a conversation. Hands, necks and arms might have been frequently washed, but as for the rest of the person...well, probably better not to ask. Washing all those heavy delicate gown would obviously be a challenge, even in the best-equipped houses.
Fashionable ladies got round the problem by wearing several layers of undergarments to protect their gowns from the...er, less acceptable aspects of being in crowed rooms with a lot of smelly people.
The first layer was a chemise, or shift, a thin garment with tight, short sleeves and a low neckline if worn under evening wearing. It was usually made of white cotton and finished with a plain hem that was shorter than the dress. They were obviously washed far more frquently than the outer clothes. Washer women of the time used coarse soap when scrubbing these garments, then plunged them into boiling water, hence the absence of colour, lace or other embellishments that would have been damaged under such treatment. Shifts also prevented transparent muslin and silk dresses from being too revealing.
The next layer was a corest, the forerunner to the bodern bra since it was designed as an undergarment that served to separate a woman's breasts. And made it impossible for her to breathe half the time, I would imagine! Short stays were often worn over the shift as well.
The final layer was the petticoat, which had a scooped neckline and was sleeveless, and was fitted in the back with hooks and eyelets. The lower edge of the petticoat was intended to be seen, since women would often lift their outer dresses to spare the delicate material of the outer dress from mud.
'Drawers' were only beginning to be worn by a few women during the regency period.
Blimey, no wonder it took ladies so long to get dressed in those days. And they had to change several times, as well!