Many people who wear silver jewelry experience black marks on their skin. This discoloration can be puzzling, leading to questions about jewelry quality or personal health. Understanding the science reveals a natural chemical process.
The Chemistry Behind the Discoloration
Black marks on skin from silver jewelry are typically silver sulfide, a compound that forms when silver reacts with sulfur-containing substances in a process known as tarnishing. Pure silver (99.9% silver) tarnishes less readily because it is less reactive. However, pure silver is too soft for jewelry, so it is alloyed with other metals for durability. Sterling silver, the most common alloy for jewelry, consists of 92.5% silver and 7.5% other metals, primarily copper. This copper content is more susceptible to reacting with sulfur compounds, accelerating tarnishing and contributing to black discoloration.
Factors Influencing the Reaction
Body Chemistry
Several factors contribute to silver leaving black marks on skin. Individual body chemistry plays a significant role, as sweat and body oils contain sulfur compounds. The unique pH level of a person’s skin can also influence this reaction, with more acidic skin accelerating tarnishing.
Environmental Conditions
Environmental conditions also impact how quickly silver tarnishes. High humidity introduces more moisture, which acts as a catalyst for the reaction between silver and sulfur compounds. Air pollution, particularly hydrogen sulfide and sulfur dioxide from industrial emissions, can significantly contribute to discoloration. Contact with certain materials, such as rubber (which contains sulfur), can also lead to tarnishing.
Chemical Exposures
Various chemical exposures can accelerate the formation of black marks. Common personal care products like lotions, perfumes, and hair products often contain sulfur, alcohol, or chlorine, which react with silver. Even some medications excreted through sweat can alter skin chemistry, promoting tarnishing. Cleaning chemicals and household products can also react with silver, causing discoloration.
Is it Harmful and How to Prevent and Remove Marks
The black marks left by silver jewelry, primarily silver sulfide, are generally harmless to the skin. While true allergic reactions to silver itself are uncommon, most skin irritation or discoloration attributed to silver is due to the presence of other metals, such as nickel or copper, in the alloy. These metals can cause contact dermatitis, leading to redness, itching, or even green discoloration, but this is distinct from the black silver sulfide marks.
Preventing black marks involves several practical steps. Keeping silver jewelry clean and dry is important, as moisture and oils can accelerate tarnishing. Removing jewelry before showering, swimming, or applying lotions and perfumes minimizes exposure to reactive substances. Proper storage in airtight containers or anti-tarnish bags, which often contain anti-tarnish strips or cloths, reduces exposure to air and humidity. Choosing jewelry made from higher purity silver, such as fine silver (99.9% pure), can also help, as it is less prone to tarnishing than sterling silver.
If black marks appear on the skin, they are superficial and can be easily removed. Washing the affected area with mild soap and water is typically sufficient to clean the discoloration. Regular cleaning of the silver jewelry itself with a soft cloth or mild silver cleaner can also prevent the buildup of tarnish that transfers to the skin.