What causes itchy dreadlocks?There are a few factors that can attribute to an itchy head, but luckily most of them can be solved the same way.
Scalp Build Up:
Every time you wash your hair you are stripping away the oils from your scalp. The more frequently you wash, the more oils your scalp as to produce. So if you normally wash your head every day and then suddenly start to wash it once a week you're going to find that your head is still producing the same amount of oils that it used to and you're getting a really irritated scalp. You need these oils, it's a balance, if you have too much you get scalp build up (this build up occurs because dreadlocks aren't quite like normal hair, with normal hair a lot of this oils get all over your hair causing you to get greasy hair. You don't really get greasy dreads, instead it all stays on your scalp and become irritating.) If you have too few oils you'll get dry skin on your head and it'll get sore and equally as annoying. This is a common problem for people with new dreads, because you'll commonly go from washing every day with normal hair to only washing maybe a couple of times a week with the new dreads and so you get a really oily head. This is why I recommend slowly altering your washing schedule in order to minimize this problem and it's covered in my "Preparing For Dreadlocks" section. In order to fix this problem you just need to get into a new washing rhythm and stick to it. Decide how often you're going to wash the hair and then keep to it. If you decide you're going to wash every 3 days then after you've been doing this for a week or so your scalp will have gotten used to producing the level of oils required for this level of washing. This is why you can find that some people wash their dreads every couple of days and some people wash theirs once a week and neither have any problems - because their dreads are used to the frequency of the washing! If you want to quickly clean up your scalp you can use a bicarb soak to break down any oils that are building up on your scalp and then change to your new routine.
This is another annoyance for those with dreads. Dandruff is when you have a dry scalp and it causes the skin to flake off and so you get little white flakes falling out of your hair and it can make the scalp itchy as they flake off. With normal hair you can fix this rather simply by buying some Head and Shoulders, unfortunately Head and Shoulders is not a residue free shampoo and therefore not recommended for dreadlocks. If you use H&S regularly with dreads you can quite quickly find that you get a sticky residue in the tips of the dreads and then lint will start sticking to the residue! To deal with dandruff I recommend a bicarbonate soak / dreadlock deep cleanse. You can either add some rosemary oil to a standard bicarb soak or you can soak your dreads and scalp in a rosemary tea. The rosemary will soothe the scalp and help prevent dandruff and the bicarb will remove any scalp build up you already have.
Not all shampoos work well with dreadlocks. If your shampoo leaves residue in your hair it can irritate your scalp. If you don't fully rinse out ALL the shampoo that you've used to wash your hair, it will remain in your dreadlocks. Dirt and lint can then stick to the residue and that can become irritating and unpleasant or the residue can dry out and flake off onto your head, drying out your scalp and again becoming irritating and unpleasant. To fix this problem I would recommend changing to a shampoo specifically designed to be residue free, I have a list of the ones I have had experience with in my "Washing and Dying" section. (Remember if you are using liquid doctor bronner's - the liquid needs to be diluted, the soap is very strong and thick straight out of the bottle and so I would recommend mixing it 1/10 with water before using it on your hair). You should then, once again use a bicarbonate soak / dreadlock deep cleanse - this will remove the soap residue that is stuck inside the dreadlocks and clean up your scalp allowing you to start fresh with your new soap. If you are already using a dreadlock soap / residue free shampoo and you are still getting build up I would recommend using less soap (I only use maybe 2 teaspoons of shampoo for my whole head) and spend longer concentrating on the rinsing out.
There are other things that can cause dread itchy-ness and each case will be slightly different but the above are the most common and people with those problems often find it hard to pin point the cause. Other issues can arise when using other dreadlock "products" such as waxes, gels and other unnecessary dreadlock additives. Also over maintaining dreadlocks by trying to tighten the roots manually can cause tightness on the scalp and irritation. If you're having scalp problems I would recommend first dropping everything other than residue-free soap/shampoo and letting the maintenance regime relax.