What is one sign of a potential allergic reaction to hair products?

Itching or swelling at the application site is a classic sign of a potential allergic reaction to hair products. When a person's skin is sensitive to certain ingredients in a product, it may respond with localized inflammation, which can manifest as redness, itching, or swelling. This condition indicates that the immune system is reacting to what it perceives as a harmful substance, making it important for users to identify and discontinue the use of the product that caused the reaction. Recognizing these symptoms early can help prevent more severe reactions and promote better skin health.

In contrast, other options, such as instant fading of hair color, might indicate issues with product efficacy or hair health rather than an allergic reaction. A strong odor from a product can be related to its composition but does not necessarily indicate a negative skin reaction. Excessive shine on the hair is generally a desired result of using certain products and doesn't suggest any allergic response. Understanding these distinctions is vital for identifying allergic reactions effectively.