What is a significant risk of using ammonia-based hair color products?

Using ammonia-based hair color products poses a significant risk of skin irritation and allergic reactions. Ammonia is a strong alkaline agent that opens the hair cuticle to enable the color to penetrate the hair shaft effectively. While this process results in long-lasting color, the harshness of ammonia can also lead to contact dermatitis, rashes, or other adverse skin reactions for some individuals. The strong odor and chemical properties may exacerbate these effects, especially for those with sensitive skin or existing allergies. This concern highlights the importance of conducting patch tests and considering clients' individual sensitivities before applying such products.

The other options, while related to the characteristics of hair color products, do not represent risks associated with ammonia usage. Long-lasting color is generally seen as a benefit rather than a risk, improved hair strength isn't directly achieved through ammonia, and cost-effectiveness is a neutral aspect of product choice that doesn't inherently carry risks.