There are a few different factors that potentially make this not a suitable practice for you: 1) The high concentration of the active ingredient is perhaps not suitable for you, which means it would be better to use a lot less of the active ingredient tablets; 2) Or it could also be the form of the active ingredient itself. Perhaps the crushed tablets are still very grainy, which can definitely be too much for your scalp and cause micro-tears when applied. 3) tablets might contain binders that don't work for your hair profile or scalp (binders - or adhesives - promote cohesiveness, as they help the other ingredients in a tablet to mix together). 4) a chemical reaction could be occurring when the tablets mix with the carrier oil. (For comparison's sake: some resilient silicones turn into no-go silicones when mixed with a cationic ingredient. While they were safe before, they turn unsafe in the presence of something else). So something similar might be occurring here. It's difficult to determine exactly what could be causing the issues you experienced as the science is very complex, and it's great that you took note of the reactions on your scalp and hair, and that you reported it to us, because it helps us understand all the possibilities. This will allow us to include it into our learning resources and help our students get better results in the end. It does seem that whatever it is, it's not working for you, sadly. If you would still like to give that a go and use Vitamin C and niacin somehow, we would suggest using liquid forms of the active ingredient (such as the ones from The Ordinary, for example). If that doesn't work, then you might just be very sensitive/allergic to those ingredients, but we'll be on the lookout for all possibilities and the right solution for you! If we do come across any additional information that might be useful about this topic, we will be sure to let you know!