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What are silicones and why are they in my hair products?

Silicones are colorless, rubber-like polymers that are typically used for lubrication in hair products, giving conditioners more mobility on the hair surface. They're in all types of products—everything from shampoos to conditioners, styling gels, leave-in conditioners, heat protectors and detanglers.

Dimethicone is the most widely used silicone in the hair care industry (it's the main ingredient in two-in-one shampoos). Dimethicones are hydrophobic, so they can protect your hair from water loss, in turn improving hair strength. A 2018 study by Leite et. al., shows that regularly applying silicone products to hair minimized breakage, increased hair compressibility, and enhanced shine.

Silicones are a major factor in your heat protection serums, creams, and sprays. They help spread the heat along your hair shaft, dispersing the impact of heat from your iron/dryer and diminishing its damage to your hair.

Can silicones build up in my hair?

"Build up" is hard to define. If you keep applying a product and reduce washing of your hair, any product will accumulate. Silicone is no different. That said, there is only a limited amount of silicone that can actually bond to your hair. Think of your hair like a stadium: each place in which silicone can bond to your hair is like a stadium seat. The stadium has a certain capacity, and while there's space in the aisles for overflow, eventually the stadium won't have any room for fans. Likewise, once the bonding sites on your hair are filled, there is limited capacity for buildup.

Understanding solubility of silicones.

Typical silicones are water insoluble, meaning they don’t like water. They do, however, like your hair. This property is great for protecting your hair and keeping it from losing water. If you've used products that contain water insoluble silicones, silicone will stay on your hair until you wash it with shampoo (you must use shampoo - rinsing with water won't work here!). Shampoos contain surfactants, ingredients that attract silicone and other oils on your hair. You need these surfactants to get the silicones off your hair.

Scientists have been working on creating water soluble silicones by attaching a molecule that likes water (water-soluble ingredients like polyethylene glycol or a protein) to one end of the silicone molecules. This makes it possible for one side of the silicone to like attaching to your hair and one side to like attaching to the water in your shower. These water soluble silicones are easier to rinse or clean off.

Can silicones be washed out?

The key takeaway is that all silicones get washed out of your hair with shampoo.  Realistically, though, it's more complicated. There are many different types of silicones, some soluble and some not. If you apply product containing water insoluble silicone and don't wash it out with shampoo, it will remain in your hair. Further, water solubility works on a spectrum: some silicones are more soluble than others and will take more rinses to wash out completely. BUT, if you use a shampoo when washing your hair, all silicones will wash out. If you use a gentle shampoo, such as a sulfate-free one, or shampoos that don’t lather well, it might require more washes to remove all silicone.

So really, whether silicones wash out of your hair and whether they build up, depends on the restrictions you put on your hair routine. If you choose a sulfate-free or low-poo routine, you should avoid water insoluble silicones. We believe it's ok for most people to use shampoos containing sulfates. Based on our analysis, low-poo or no-poo shampoos are more harmful than helpful, but we’ll do a post soon on the topic.

So, should I avoid silicones?

If you want to know if silicones will build up in your hair, you need to answer two questions.

1. Am I washing my hair at least once per week with a shampoo?

If yes, then silicone is not going to build up because, no matter what type of silicone, surfactants in your shampoo will wash off the silicones. And in this case, even your shampoo and conditioner can include silicone. Some of the most common silicones are not water soluble, meaning they cannot be washed out with a simple water rinse. So if you are someone who does not shampoo (which we don’t recommend) then avoid water insoluble silicones. We'll publish a blog post shortly that lists those to avoid.

2. Do I have thin hair?

If yes, it might be that the amount of silicone you do accumulate between washes is too heavy for your hair. This might cause your hair to feel weighed down and hard to style. Silicones are typically heavier than the other ingredients in your products. However, thin hair is generally easy to weigh down. It requires that you're more careful about the amount of product you apply and the way in which you distribute it.