Gold

Gold used for piercing jewelry shouldn't be of a quality lower than 14K or 18K (58% to 75%).

Gilded jewelry is not recommended for longer wearing, especially not for fresh piercings.
Gold jewelry is often not autoclave-sterilised because discoloration might occur.

Gold is a very soft material and easily damaged, which can lead to skin irritation, especially with fresh piercings. Instead of gold, during the healing period it's recommended to wear Zircon gold titanium
jewelry or a combination of titanium base and golden extension.

Allergies to gold are rare but they exist, so the gold used for jewelry should be of a high quality.