Does dyeing hair with scalp scabs cause cancer?

In general, whether hair dyeing causes cancer when there is scalp crusting needs to be comprehensively evaluated based on specific circumstances. If in doubt, it is recommended to consult a professional doctor or dermatologist. The detailed analysis is as follows:

When crusting results from minor abrasions, and the area has become stable, dry, without redness, swelling, or exudation, and other parts of the scalp remain intact, the cancer risk associated with hair dyeing is not significantly different from that of healthy scalp. Such crusts maintain an intact protective barrier, preventing large amounts of hair dye chemicals from penetrating beneath the skin. Provided that certified products are used, the procedure is performed quickly, and the scalp is thoroughly washed afterward to minimize chemical exposure time, the likelihood of increasing cancer risk is generally low.

However, if the crust is in a state of breakage or inflammation—such as when accompanied by itching, redness, swelling, or discharge—or if it stems from conditions like seborrheic dermatitis or folliculitis, hair dyeing may increase health risks. Damaged scalp cannot effectively block the chemicals in hair dyes, allowing components to more easily enter the bloodstream. This not only may worsen inflammation but also increases the chance for harmful substances to interact with body cells, thereby elevating the potential cancer risk.

After scalp crusting appears, the underlying cause should first be identified and proper cleansing maintained. Gently wash with mild shampoo, avoiding scratching or irritation. Before complete healing, keep the scalp dry and clean to minimize external irritants. It is advisable to delay hair dyeing until the scalp is fully healed with no signs of wounds or inflammation, thus reducing risks at the source.