If you notice redness, itching or any discomfort where the cord or stone touches your skin, remove the pendant immediately. In many cases, this type of irritation is mechanical — friction from the cord, trapped sweat or moisture under the stone — rather than a sign of a specific allergy to shungite. Still, natural does not mean irritation-free for every person, so treat any reaction seriously.
After removing the piece, keep the area clean and dry and give your skin time to settle. If the irritation clears and you want to try wearing it again, adjust how the pendant sits: keep the cord from rubbing the same spot all day, and take the pendant off during sleep and exercise so the skin underneath can breathe. If the irritation comes back, the better choice is simply not to wear the pendant.
The product information is clear that this is an accessory, not a medical product. If you have a chronic skin condition, or if the irritation does not settle after removal, consult a specialist rather than experimenting with the pendant or applying products that are not meant for that situation. For most people, stopping wear is enough, but persistent discomfort should always be checked by a professional.