Each pass of a razor blade across the skin removes the hair shaft but also scrapes away part of the stratum corneum, the protective outermost barrier layer. When this barrier is compromised, nerve endings sit closer to the surface and inflammatory mediators are released, producing the stinging, redness, and warmth you feel after shaving.
Dull or contaminated blades multiply the problem because they drag and tug instead of cutting cleanly. Dry shaving, shaving against the direction of hair growth, and pressing too firmly all add friction, micro-tears, and follicular trauma that intensify the inflammatory response. The American Academy of Dermatology identifies blade dullness, dry shaving, and improper technique as the primary drivers of post-shave irritation.
People with sensitive or reactive skin, eczema-prone skin, or curly coarse hair tend to react more strongly because their barrier function is already lower at baseline. Permanent laser hair removal to end razor burn removes the need to keep traumatizing the skin every few days.
