SOME INERT CHEMICALS AND CHEMICALS THAT COMMONLY CAUSE REACTIONS
Some chemicals are very inert, and do not cause reactions. They do not give off vapours at all. Substances such as glass, china clay, cement, ceramics, clay, stone, marble, cork and non-resinous woods do not cause reactions. If other chemicals (such as varnishes) are used on them, then they can cause reactions, or if you are exposed to heavy levels of dust, you can get irritant reactions, but they virtually never cause sensitivity.
Metals can cause allergy, but do not cause sensitivity. Some chemicals are extremely simple in their chemical structure, as well as being inert, and again do not cause reactions – for instance, sodium chloride (ordinary salt), sodium bicarbonate, Borax and washing soda. Additives in table salt sometimes cause reactions, but pure sodium chloride dcas not.
There are three prime characteristics of those chemicals that commonly cause reactions. One category includes chemicals that are highly toxic at high levels of exposure, such as chlorine, ammonia and benzene. The second category is chemicals with complex structures, which appear more prone to cause reactions than other chemicals, for instance, complex hydrocarbons, such as organic solvents or many fragrances. Thirdly, and most important, are chemicals that release vapour or are more volatile so that they are readily inhaled or absorbed into the system.
It is worth emphasising that natural chemicals can be as troublesome as synthetic chemicals. Some natural chemicals (especially those that are volatile, give off fumes and have complex structures) can be very troublesome. These include natural plant oils and fragrances, such as menthol, lavender oil, oil of wintergreen, oil from orange or lemon peel; resins such as natural turpentine or rosin; terpenes such as grass sap; and other natural vegetable and plant products such as latex, acetic acid (vinegar), Balsam of Peru (a flavouring and perfuming agent), pyrethrum and derris (used as pesticides in organic gardening).
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