A conditioner-filler is often used when doing a chemical relaxer retouch because the hair chips and cracks during the process of relaxing. When someone chemically relaxes their hair, they strip a protective layer away from their hair. This causes the chips and cracks mentioned earlier. The chemicals used can also affect how much the hair chips and/or cracks when it’s being chemically relaxed. Conditioner-filler, or protein-filler, can be used to fill these cracks. It can also be used to keep hair healthy after being relaxed by being the first thing you use in the shower.
Chemically relaxed hair is very prone to damage. Right after it’s been relaxed is when it’s weakest, so the use of a conditioner-filler is often recommended and the stylist may even send you home with some recommendations of which brands work best for your type of hair.