Frame Materials and Metal Allergies
1. What is "metal allergy?"
Habitually wearing accessories or spectacles, for example, results in the metal constituent of such items dissolving, although only slightly, due to contact with perspiration and other bodily fluids, with the result that ionized metal will penetrate the body. Once this happens, coming into contact with the same metal again will result in rejection, in some cases causing a rash on the skin (allergic contact dermatitis). This condition is known as "metal allergy." Like pollen allergies, metal allergy is the result of a reaction by our antibodies.
To explain this phenomenon in greater detail, when the body absorbs metal ions, it produces antibodies to eliminate these ions and, the next time the same metal ions are absorbed by the body, the antibodies produced the first time react violently to the metal ions, resulting in the body experiencing symptoms such as inflammation, itchiness or pain, an effect identical to the symptoms resulting from the reaction of the white blood cells to pathogens that enter the body.
The result is that prolonged contact of the skin with accessories such as necklaces, for example, will make it more likely that the wearer will suffer an allergic reaction to metal. Furthermore, spectacle frames may also cause an allergic reaction to metal depending on the material from which they are made.
2. What metals cause metal allergies?
The most common cause of metal allergies is mercury, and this is followed by metals including nickel, cobalt, tin, palladium and chrome.Conversely, metals such as gold, titanium, silver and iron are less likely to produce allergic reactions since they rarely dissolve upon contact with perspiration or other bodily fluids.
Of the metals most likely to produce allergic reactions, nickel is the one that is most commonly used in spectacle frames. For a long time, nickel has been used in the form of an alloy as a material for spectacle frames and is also used as the base plating material for plating and gold plating, for example.
Compared with other metals, the properties of nickel make it readily dissolvable, and this means that contact of the body with nickel will result in the metal beginning to dissolve due to the effect of sodium ions in perspiration, causing an allergic reaction.
However, as a recent measure to prevent allergic reactions, the materials used in many products on the market nowadays are nickel-free. In addition, frames with vinyl-covered temples are now available for people with metal allergies.
People who may have metal allergies are recommended to undergo a patch test at a dermatologist. Forearmed with knowledge of which metals are likely to cause an allergic reaction, you will know which metals to avoid when purchasing spectacles.
3. Information about Frame Materials
Broadly speaking, the following four types of material are used in spectacle frames.
"Metal frames" is a general term used to refer to frames made from metals such as copper alloys. Light, robust titanium, delicate copper alloys that can even be engraved: hardness is a characteristic to all these materials. Recent improvements in surface finishing have produced a wide diversity of coloring. Metal frames are the most likely to produce allergic reactions. In particular, it is important that people concerned about allergies ascertain what material the frames are made from when choosing frames for their spectacles.
These are non-metallic frames made from plastic. The term "celluloid frame" may be more familiar, but recently, celluloid has been replaced by materials such as acetate, so the term "plastic frame" is more accurate. Since celluloid is prone to discoloration or cracking when exposed to ultraviolet rays, it is rarely used nowadays. Acetate looks a lot like celluloid and, although it is inferior to celluloid in terms of elasticity, it is lighter and much less combustible. Moreover, compared to metals, celluloid and plastic give a greater sense of warmth. Plastics also offer a wide range of variations realized by combinations of base material colors and patterns, for example, transparency or frosted glass effects. Needless to say, plastics present no risk of metal allergies.
Pure frames give a sense of rarity unique to the precious metals from which they are made such as 18 K, 14 K, white gold or platinum. Although heavier than titanium, such materials excel in terms of the gentle feeling on the skin and their decorative qualities. Of course, designs differ depending on one's sense of values based on whether one sees pure materials as expensive accessories or simply as a material, and you can see designs including not only gorgeous elaborate items, but also frames that give a sharp, classic impression.
As well as the above, combinations of different materials such as metal and plastic or metal and 18 K materials and new materials are being developed one after another. In addition, tortoiseshell, a natural material that has become even more valuable since its import was banned under the terms of the Washington Convention on International Trade in Endangered Species of Wild Fauna and Flora, is light, pliant and strong and its deep luminescence and luster imbues it with the air of an objet d'art.
4. Evolving Frame Materials
Frame materials are also evolving day by day. Of all the newly-emerging materials, the following two materials are particularly worthy of note.
There is no doubt that titanium has nowadays become the focus of attention as a frame material. It has been determined that titanium presents almost no risk of allergic reactions in people suffering from allergies and it offers the advantage of being only approximately half the weight of iron. It is lighter and softer than stainless steel. Not only that, but it does not rust even if immersed in seawater, and is not prone to discoloration. The advantages of titanium are its "lightness," "strength" and "rust-resistance." That having been said, titanium does have one disadvantage: It is difficult to process. In addition, it quickly oxidizes, making processes such as soldering (joining metal to metal with wax) and surface treatment difficult. Nevertheless, thanks to recent advances in technology, titanium spectacle frames are now widely used.
The most popular titanium alloy is β titanium (e.g. Ti, aluminum, vanadium). Because of its outstanding durability, β titanium allows delicate, light designs, and improvements have been made in its springiness. Developments of titanium alloys have produced a wide diversity of new materials such as shape memory alloy (springiness) and biocompatible metals (biocompatibility). Other materials include aluminum and carbon.
It is only natural that we should focus on design when selecting a pair of spectacles.
However, a pair of spectacles is an item that is in direct contact with our skin every day. Taking into consideration not only the design, but also the properties and characteristics of the frame materials will undoubtedly help you find a unique pair of spectacles ideal for you.