I'm rewriting my intitial review of this product because I'm not sure that I explained myself or the product well enough the first time around. This 4 Day Straight Flat Iron Spray is marketed as a touch up to be used between their 14 day Keratin treatment. I've never used their Keratin treatment and can't comment on how well it works but this is essentially a heat activated protein treatment that you bake in with a flat iron. The bottle says to dry hair completely then spray small sections of your hair, straightening each section while sealing this in with your flat iron. On the suggestion of a Drugstore.com reviewer and because I'm a bit over cautious with flat ironing I chose to use this as a blow out spray on damp hair first and then made a quick pass with my flat iron to seal it in completely after my hair was dry. It worked great and gave me shiney, straight, frizz free hair that lasted through a rainy day even though I did not follow the directions on the bottle. It doesn't recommend how often to use this and says that it lasts for 4 days or until your next shampoo. This is where I have a problem and removed a lippie. From what I understand protein when overused will make your hair brittle from overload. I can see this being an issue if this product was used all of the time. After washing my hair the first time I could feel the difference in my hair texture and needed a decent panthenol based leave in to make it feel soft. This did not wash out after my first shampoo. I'm fine with that but had I tried to use this multiple times in a week with that much heat I'm thinking my hair would have been feeling like burnt straw. I still have tons of shine, no frizz and a much faster blow dry so I'm happy to wait it out a bit. Past experience with protein treatments tells me that it will be almost two weeks before I can safely load my hair up with that much protein again. Will it keep my hair straight and frizz free no matter the weather like the day I applied it ? No but I expect it will make my life easier and my hair look healthier for a couple of weeks. If you're looking for Brazillian straight hair for a special day this will do it. Every day? Go to a professional. This is an excellent at home protein treatment that I would never use multiple times a week but well worth the ridiculously cheap $5.99.