Yes, and many people do, because there is a certain bleaching range between knots that are dark enough to show, and knots that are overbleached, potentially causing the unit to have a shorter useful life. In general, the factories err on the side of caution, but many hair wearers would rather sacrifice durability for increased realism.

So if you decide to give it a try, at your own risk of damage or loss, here are simple instructions for the best method of bleaching knots on a lace hairpiece.

1. Buy white powder bleach from the beauty supply store and either 20% or 40% gel developer. Avoid cream developer as it's too watery and do not use liquid developer.
2. Mix  bleach powder and gel developer in equal quantities in a plastic or glass bowl with a nylon dye brush. (no metal).
3. Paint the resulting paste onto the underside of the lace. The gel is thick enough so it won't flow through the lace and lighten the whole hair.
4. After 10 or 15 minutes (visually check), wash it out from the top side and then shampoo the unit.