Rule 13 of 40 · Chapter II — The Body and the Current
Dry skin is not insulation
Why this rule exists
People trust their skin to protect them, and dry, intact skin does add real resistance. But it is a thin, unreliable barrier. Sweat, water, cuts, or just firm contact pressure can drop hand-to-hand resistance from tens of thousands of ohms to around a thousand, enough to turn a startle into a lethal current at ordinary voltages. Skin resistance also falls as current flows and heat builds. Counting on your skin means counting on the least predictable variable in the circuit. Insulate with rated gloves and tools, not the hope that your hands are dry.
In practice
Provide the insulation yourself rather than relying on skin. Wear electrical gloves rated for the voltage when contact with live parts is possible, and keep them inspected and dry inside. Use tools with intact, rated insulation. Keep your hands, gloves, and the work area dry; wipe sweat, and do not work with wet hands or on damp surfaces. Remove metal jewelry that shorts across your skin's resistance. And where practical, de-energize so your skin's resistance never has to matter at all.
When it doesn't apply
Rated rubber gloves and insulated tools have voltage classes and inspection intervals; a nicked glove or cracked handle offers no protection and can be worse than none by giving false confidence. Skin condition is never a substitute for proper insulation. If the voltage or energy exceeds what your gloves and tools are rated for, that is qualified work, so stop.