Originally Answered: Is this African-American hair myth true? Also, what type of shampoo/conditioner?
What you use on your hair will depend on your hair type. If your hair is not naturally curly then you might want to find something other than mixed chicks, because that's for people with curly hair. Curly hair tends to be dryer than other hair types. The curlier it is then the dryer it is. If you're hair is not naturally curly then you wouldn't use the same products as someone with curly hair. Your true hair type is what your hair looks like when it's dry, not damp or wet.
Your grandma is wrong. There are a lot of myths floating in the black community regarding proper hair care. Unfortunately, hair abuse is probably the number one cause of why you don't see many blacks with mid-back or waist-length hair. People with relaxers need to grease/oil their scalp because relaxers dries out the hair. Others also oil/grease their scalp because they just have a very dry scalp. I haven't had to put anything on my scalp since I was relaxed, and I've been natural for about 11 months, and I only need to put moisturizer on my hair, not scalp. And, on top of that, how often your grease your scalp depends on how quickly it dries. My sister can go a long while without putting anything on her scalp, although she might want to do it more often since she suffers from flaky dry scalp, haha, but she could go much longer than 2-3 days without greasing.
Organic and natural shampoos are usually the best for your hair because they don't contain harsh ingredients. I use Wen cleansing conditioner, which is not a shampoo, and this cleans my hair and leaves it very moisturized. Regular shampoos dry out the hair because they contain sulfates. Organic/natural shampoos do not contain this harsh ingredients and your hair will retain some moisture, which means you can wash more often without completely stripping your hair of oil. These types of shampoos can be found at health foods stores, Walgreens, online, and other brick-and-mortar stores. Most that you find on the shelves are not 100% certified organic, but Dr. Bonners is an example of a bar shampoo that is 100% certified organic. Some have a high percentage of organic ingredients like Yes to Carrots and Giovanni. They're both certified organic and are completely natural, but they are not 100% organic (confusing? lol). They don't need to be 100% organic to be certified organic (just a high percentage of organic ingredients). There are many on the market and you will have to experiment to find the right one(s) for your own hair, which is why I don't have any recommendations.
Yes, most blacks tend to have extremely dry hair because our natural hair is the curliest, you'd be hard pressed to find another race with hair that's as curly as our, and the curlier your hair is then the drier it will be. And, the drying relaxers that most blacks use is another reason. Also, what the other person said about oil glands - it's difficult for the natural oil to travel down an extremely curly hair strand, so it doesn't reach the ends of the hair and leaves the hair very dry, whereas those with straight or wavy hair won't really have this problem and can suffer from hair that's too oily.
Technically, those who don't use shampoo will still have to clarify their hair to get rid of the build-up and ingredients that conditioner alone cannot get out. Clarifying can be with a clarifying shampoo or conditioner, or homemade ingredients like adding baking soda to their conditioner and this strips their hair to get rid of all the dirt and grim that conditioner alone cannot get out. Also, there's low-poo, people who condition most of the time and will use shampoo like once a week to once a month in order to completely clean their hair.