Citric acid is a natural ingredient found in citrus fruits such as lime, lemons, oranges, and grapefruits. It is commonly used as a pH regulator. Citric Acid is often used in hair product formulations to bring the pH levels down, which helps reduce frizz. By helping to stabilize the pH of formulations, citric acid can contribute to the longevity of cosmetic products. The pH of a product can affect how some preservatives work, so citric acid ensures optimal stability for a product.