Wooden blocks are durable and when properly cared for can last for generations.  I have blocks that are over 50 years old and are still being used, by my granddaughter.

Your blocks are not finished.  They are plain wood, cut and sanded, no paint, varnish or oils have been used on the wood.  

Clean wooden toys by wiping with a dry cloth first. If a damp cloth is needed to remove dirt, moisten the cloth just to clean. Wipe away moisture and let air dry.  

NEVER use furniture polish on blocks. Furniture Polish contains toxic substances that may be harmful if swallowed by children.  

Water is wood's worst enemy.  Don't let the blocks sit in water. If the blocks gets wet, dry them off with a dry towel and let the block air dry.  

The blocks will get small dents from use. This is to be expected with normal use.  

If the blocks get ruff, usually from exposure to water, you can sand them with 220 grit sandpaper to smooth them again.  Available at most harware stores. 

To disinfect the blocks, use vinegar and rinse with water.