What is a common symptom of an allergic reaction to hair products?

A common symptom of an allergic reaction to hair products is a skin rash. This occurs because the body identifies certain ingredients in the hair products as harmful, triggering an immune response that can lead to localized inflammation and irritation. The skin might become red, itchy, and develop bumps or hives in the area where the product was applied.

Hair loss, while potentially a concern in various contexts, is not typically a direct symptom of an allergic reaction. Instead, it may arise from other issues like stress or hormonal changes. A dry scalp, on the other hand, can result from various factors such as weather and product use, but it is not a specific indicator of an allergic reaction. Lastly, a foul odor might be associated with certain types of hair products or scalp conditions, but it does not indicate an allergic response. Thus, the observation of a skin rash is a clear and significant sign of an allergy stemming from hair products.