Which type of lightener is usually stronger and should not be used directly on the scalp?

The correct answer to this question is that stronger lighteners that should not be used directly on the scalp are typically off the scalp lighteners. These lighteners are designed for use away from the scalp, often for full hair bleaching or highlighting techniques. They contain a higher concentration of bleaching agents, which makes them more potent and potentially irritating to the sensitive skin on the scalp.

Off the scalp lighteners are primarily used for techniques that require a stronger lift, such as foiling or balayage, where the product is applied to strands of hair rather than the scalp area itself. This method minimizes the risk of scalp irritation while still achieving the desired level of lightening in the hair.

In comparison, on the scalp lighteners are formulated specifically to be safe for direct application to the scalp, typically containing gentler ingredients and lower concentrations to avoid irritation. Powdered lighteners, while they can be strong, can vary in formulation and may or may not be suitable for direct scalp application, depending on their specific properties. Gel lighteners are often designed for ease of application and can also vary in strength, but they are usually formulated with a lower pH to be safer for scalp application as well.