Pearls are an organic gem that require more specialised care than most other gem materials. They deteriorate in contact with chemicals like household cleaners, perfumes, cosmetics, and hair care products of all kinds.

A good rule of thumb is that pearls are the last thing you put on when dressing and the first thing you take off when you get home. Never apply perfume or hair spray when you are wearing pearl jewellery.

The surface of a pearl is soft and can be easily damaged. Pearls set in rings and bracelets are subject to more scuffing and scratching than pearls set in brooches, earrings, necklaces or strands.

Main Care Tips
Never clean pearls in an ultrasonic cleaner. Never use detergent or bleaches or baking soda or ammonia based products. Do not use scouring pads or abrasive materials to clean the pearls. Take your pearls off when applying cosmetics and perfumes. Do not keep pearls near heaters or in places that get strong sunlight, such as a window sill, they'll dry out. 

Cleaning Tips
Caring for your precious pearls is easy. It is best to put your pearls on last. Cosmetics, perfumes, and hair spray all contain chemicals that can dull the lustre of a pearl over an extended period of time. Periodically wipe your pearls with a soft damp cloth.

Storage
Pearls should be stored separately from other jewellery because of the pearl's soft surface which can be easily scratched by other gems. A silk bag, velvet-lined box, or similar are good places to store pearls. 
Never store pearls in a plastic bag. Some types of plastics emit a chemical that can cause the surface of the pearls to deteriorate.
Pearl strands should be stored flat rather than hung to avoid premature stretching of thread..