Vanessa Thomas, cosmetic chemist, and founder of her company Freelance Formulations shared, “Certain ingredients can cause people to have reactions of varying degrees. Whether or not a specific ingredient causes hair loss is difficult to ascertain. However, overuse of some products with certain ingredients can cause problems of varying degrees to people depending on their hair type and the product type.” She went on to explain that a common cause of hair thinning in conditioners is silicone, especially silicones that are not water-soluble.
“This is because silicones form a barrier around the hair shaft, to protect the hair as well as improve the texture. Silicones can weigh down hair if used excessively, and some are considerably hard to wash out. Thinning hair does not hold heavy products well, and this can make thinning/fine hair look greasy and unkempt.”
Silicones can cause trouble beyond hair thinning—they can also lead to hair breakage, as your hair could become more brittle.
Thomas added, “Hair breakage can also happen when the hair is not getting enough moisture or being heated too much.” She cautioned that silicones don’t need to be removed completely, but that people that have hair that is already thinning out, should use these products less, if at all.