Because pearls are considered an "organic" gemstone, they do require more care than a gemstone such as a diamond would.
Pearls should be protected both during wearing them and while storing them. They are susceptible to reacting with the acids and oils in our skin, the perfume we may wear, as well as the makeup we may use. Because of this it is an adopted rule that your pearls are the last thing you don and the first thing you remove, to avoid exposure to substances that could damage their lustre.
After wearing, take the time to clean your pearls with a soft cloth that has been dampened in clean cool water, followed by rubbing with a dry cloth. The use of distilled water is advised because there is a lack of mineral substances which can deposit on the surface of pearls and weaken the pearl luster. When not worn for extended periods, at regular intervals the pearls should be wiped with a soft cloth dampened in clean cool water and carefully rubbed dry. You can use a soft bristled toothbrush to remove stubborn grime from the surface of the pearls as long as you use care and don't scrub too hard.
Store your pearls in jewelry pouches, cloth bags, or a jewelry box. Keep items separated to avoid scratching. Pearls contain 2-4% water. Store them in a cool place and if possible, adding a small damp piece of linen in the bag with them will help them maintain their moisture level to help prevent them from drying out, cracking and turning brittle. Never store pearls in a plastic bag or plastic container as the plastic could very well contain chemicals that could react badly with the pearls causing the surface of the pearl to deteriorate.
Fading can occur in pearls when exposed to strong lights for extended time periods, such as strong natural and artificial light, or to strong lighting in a display case. Avoid leaving pearls laying out on a dresser or table exposed to such lighting for any length of time.