For me, it seems to depend on what product it's in. It seems to be in nearly every new product I've tried, and I'm not having any problems, but many eons ago, when I tried Pantene, I had major problems, and a hairdresser eventually told me it was the Panthenol. I'm using a product now with Panthenol, though, and my hair is really curly, so I'm going with the product theory. It probably depends on what other ingredients it's combined with.