I’m sorry to hear about your buildup problem. From the sounds of it, you certainly have something inside of your locks that shouldn’t be there! It’s hard to say what exactly it is without a photo or hands-on look, but it’s likely soap residue, dead skin, or a combination of the two. The only way to know for sure is to pick out the end of a lock with the throat of a small crochet hook or the end of a rat tail comb and take a look for yourself.
You have a few options to remove the buildup. My primary suggestion is to watch this video on buildup removal by Quotidianlight on YouTube. The second suggestion is to rinse your hair very, very well with hot water for a week or so—a pressurized shower head may help. Also try a Deep Clean.
Lastly, the only way to really get rid of it all is to brush your locks out. Of course, this is a bit of an extreme measure, so I don’t really suggest it.
If it’s skip buildup, dead skin cells aren’t harmful to your hair. They are all over your house, in your clothes, and on other places of your body. While it isn’t the most desirable thing to have in your hair, just know that it isn’t a bad thing. Everyone with locks has some number of skin cells in their hair; its unavoidable. In the future, you can prevent excess skin buildup in your new growth by managing dry scalp.
If it’s shampoo residue, then it could potentially harbor moisture and encourage mildew. But if you are careful to keep your hair dry whenever possible, it shouldn’t be too much of a problem.
Even if you are dissatisfied with the lower parts of your locks, there is always hope for your new growth. So if you are really attached to them and don’t want to brush them out, you can just make sure your new growth comes in clean and slowly trim off the built-up ends over time.