Pearls are so delicate that cleaning them is not recommended. However, if it becomes necessary, use a tiny bit of mild detergent on a damp cloth, but make sure to wring out most of the water. Wipe the pearls very gently in each direction. Afterwards, use another soft, barely damp cloth to remove any soapy residue. You may need to do this several times.
Mikimotoamerica.com cautions against using ultrasonic cleansers, since they can damage pearls. Keep any home cleaning as brief as possible. Too much cleaning can dull the luster. Water can weaken the silk threads used to string them. Avoid dipping pearls in water, and don't wear them while swimming or bathing. For best results, take them to a jeweler or pearl specialist to be cleaned and repaired.
The nacre coating on cultured pearls is fairly porous. Sweat, cosmetics and hair products can damage the surface. Vinegar, fruit juice and detergents can also erode it. If any of these come in contact with your pearls, wipe them with a soft cloth. Since sharp objects and gemstones can scratch them, lay the pearls flat, and store them apart from other jewelry.
Pearls that aren't worn for long periods can get dehydrated, so wear them often. Natural skin oils enhance their luster. Wearing dull pearls for a few hours can help them shine again.