Preservatives are meant to be used in very specific dosages — too much can irritate the scalp and doesn’t make the product “extra safe.” Stick to the recommended amount from our help widget and use only potassium sorbate, as it’s one of the most gentle alternatives you can find for homemade products. Tip: Since your scalp is red and itchy, it might be good to: Take a break from daily washes with Shampoo A and alternate with a very gentle rinse (just water or a diluted shampoo). Test your scalp’s reaction by using aloe as a short mask before washing, rather than leaving it on daily. Maybe consider only testing one product at a time for a few days in a row so you can determine more clearly what’s working for you and what isn’t!