Pay close attention to the type of cleaner you use on the acrylic. Alcohol-based cleaners can be damaging to plastics — acrylic / plexiglass  is a type of plastic. Ammonia-based cleaners, such as Windex will cloud the plexi. Many common glass cleaners contain some amount of ammonia, so take care to read the label before using.

Spray ammonia-free cleaner or special plexi/acrylic cleaner onto cloth. NEVER spray cleaner directly onto the plexi. Other common cleaning ingredients can seep through the frame and damage the art or photo. If you do not have an ammonia-free glass cleaner, use a mixture of mild soap and water. Be sure to use a microfiber cloth in order to avoid leaving scratches in your plexiglass.