When it comes to hair care, a one-size-fits-all approach just doesn't cut it, and that's certainly the case when it comes to conditioning low porosity hair, which tends to have a harder time retaining and absorbing moisture. But you'll find the best deep conditioners for low porosity hair are lightweight, made with ingredients that can actually penetrate the hair shaft, and will — or won't — make use of protein, depending on your specific needs.
One of the signs of low porosity hair is an inability to retain moisture due to closed cuticles that make it difficult for certain oils and conditioners to sink in. That's why it's important to look for conditioners made with ingredients that can actually penetrate the hair shaft, as opposed to just coating it. Your best bet will be conditioners made with moisturizers like coconut oil, argan oil, sweet almond oil, and shea butter, all of which can sink in deeply to deliver hydration.
Another important ingredient to be mindful of is protein, which can be a pro or a con, depending on your hair. If your hair has seen frequent washing, heat styling, coloring, and processing, it might be weak and prone to breakage and hair fall — in that case, it's a good idea to shoot for a protein-rich conditioner to rebuild strands. On the other hand, protein-sensitive hair (which has plenty of protein already) is likely to be dry and brittle, and a protein conditioner is likely to leave low porosity hair even more sapped for moisture. If that's you, opt for a protein-free formula.