What is a potential side effect of coloring hair?

Choosing the option about allergic reaction or scalp irritation reflects an essential understanding of the potential risks associated with hair coloring. Hair dyes contain a variety of chemical compounds, some of which can cause allergic reactions in sensitive individuals. Symptoms may include redness, itching, swelling, or even severe reactions such as difficulty breathing in extreme cases. Scalp irritation can also occur due to the chemicals in the dye, which might lead to discomfort or a burning sensation on the scalp.

The other options don't accurately represent common side effects of hair coloring. Immediate hair loss is not typically associated with coloring; while hair dye can weaken hair over time if misused, sudden loss is not a standard reaction. Likewise, increased shininess of hair and improved texture are generally considered cosmetic benefits rather than side effects. While it's true that some dyes may enhance shine, this is not a guaranteed or universal effect and doesn't classify as a side effect. Thus, the most appropriate and accurate answer is the potential for allergic reactions or scalp irritation.