Sin sal is Spanish for without salt, and shampoo sin sal is how a lot of people search for salt-free shampoo. The phrase took off alongside keratin smoothing treatments. Allure covered the Brazilian treatment when it first arrived in the US from Brazil in the mid-2000s, and the aftercare advice that came with it has stuck: wait a couple of days before washing, then use a shampoo without sulfates and without salt.

Here is what the salt actually does. In many shampoos, sodium chloride, plain table salt, is used as a thickener, especially in formulas with sodium lauryl sulfate. It does not clean your hair. It just makes the liquid feel richer in your hand. Stylists say it shortens the life of a keratin treatment. That is salon wisdom rather than a lab finding, but it is consistent enough that most smoothing brands build their aftercare around it.

So for this edit I read the full ingredient list of every shampoo in the first grid and kept only formulas with no sodium chloride and no sodium lauryl or laureth sulfate. Some use milder cleansers instead, which I note below.

The first grid is eight salt-free shampoos from Keratin Complex, Kristin Ess, Moroccanoil, Briogeo and Verb. The second is conditioners, leave-ins and a smoothing cream that keep treated hair smooth.

My tip: read the ingredient list, not the front label. Sodium chloride usually sits near the end, and it turns up in plenty of bottles that call themselves gentle.

Keratin Complex is the smoothing-treatment brand here, and its two shampoos are the only ones in this grid made specifically for keratin-treated hair. The Color Care Smoothing Shampoo is color-safe and gently cleans while minimizing frizz, and KCHYDRATE Moisture Shampoo adds proteins, amino acids and vitamins for softness. Both skip salt and the harsher sulfates, though they do use milder cleansers.

Kristin Ess+ Peptide Boost Volumizing Shampoo is the pick for fine hair that falls flat after smoothing, and it has no sodium chloride.

Moroccanoil has two. The Hydrating Shampoo is a daily argan oil formula for dry hair, and the Moisture Repair Shampoo adds protein for weakened, damaged hair.

Briogeo's Farewell Frizz Smoothing Shampoo uses rosehip, argan and coconut oils to fight frizz, which makes it a natural match for smoothed hair. The Superfoods Banana + Coconut Nourishing Shampoo is for dry hair.

Verb Hydrate Shampoo is for dry, frizzy hair, with argan and babassu oils.

A test before you buy anything new: flip the bottle and look for sodium chloride in the ingredient list. If you see it, keep looking.

What I would skip: clarifying shampoos for the first few weeks after a keratin treatment. They are designed to strip buildup, and a fresh treatment is exactly what you want to keep.

Keratin Complex Keratin Care Smoothing Conditioner is the daily partner to the Keratin Complex shampoos, made to fight frizz, and the KCTEXTURE Leave-In Conditioner seals in moisture for curls and waves.

Moroccanoil Frizz Control Conditioner fights frizz, flyaways and static, and Moroccanoil Smoothing Lotion is a nourishing styling cream that controls frizz and makes hair easier to manage. It is the one I would use on air-dry days.

Olaplex has three. No.5 Bond Maintenance Conditioner is a concentrated conditioner for medium to coarse hair that repairs everyday damage. No.5L Moisturize & Mend is a leave-in that keeps working after you rinse. No.6 Bond Smoother is a styling cream the brand says controls frizz for up to 72 hours, which is a good fit for anyone stretching the time between blowouts.

Briogeo Farewell Frizz Rosarco Milk Leave-In Conditioner is lightweight and locks out humidity, so it is the one I would reach for on fine hair or in a humid summer.

A tip for treated hair: use a leave-in every time you wash, even if your hair feels smooth. Smoothing treatments make hair behave, but they do not replace moisture.

What I would skip: heavy oils right after a treatment. Let the hair settle for a week, then add oil if you need it.

I think shampoo sin sal is one of those small switches worth making if you have had a keratin treatment. Salt is not the only factor in how long smoothing lasts, but it is an easy one to control. Start with a Keratin Complex shampoo if you want the formula made for treated hair, or pick the salt-free shampoo that suits your hair type from the rest of the grid. Add a leave-in, go easy on heat, and read every label.