One of the issues that people with naturally curly hair have to contend with is overly dry, frizzy hair, even after adding a lot of moisture. More than likely, this is due to having highly porous hair. Hair porosity is the ability of your hair to be able to hold onto moisture. Curly hair has generally higher levels of porosity, but damaged and chemically treated hair has raised and open cuticles, resulting in excessively porous hair that loses moisture very quickly. While damaged hair is irreversible, some simple at-home solutions can temporarily seal your cuticles to help control your hair's porosity levels.
Use protein-based conditioners when washing your hair. Protein helps to fill in gaps in the cuticle and seal in moisture while also strengthening your hair. Look for conditioners containing ingredients such as keratin, silk, wheat, collagen or vegetable proteins.
Give your hair a protein treatment for very dry, damaged hair. You can find ready-made protein treatments at beauty supply stores, but you can also make your own at home. Add an egg or some mayonnaise to a regular conditioner to give it a protein boost. Leave the protein treatment on for at least 30 minutes before rinsing it out, and follow up with a deep moisturizing conditioner, as too much protein can dry out your hair. Keep protein treatments to no more than one per week.
Rinse your hair with an apple cider vinegar rinse. The enzymes in apple cider help to close open cuticles to help your hair retain moisture. Combine 1/4 cup of apple cider vinegar with 2 cups of water to make the rinse. Deep condition your hair before doing the vinegar rinse, then rinse out immediately with cool water.
To determine your hair's porosity levels, hold out a strand and slide your fingers from the root to the end. If the hair feels slightly bumpy, or rough you have overly porous hair. If it feels smooth, you have normal porosity. Hair that feels very slick could be a sign of low porosity, meaning you may need to deep condition your hair more often.