Irritation in organisms
a In higher organisms, an allergic response may be the cause of irritation. An allergen is defined distinctly from an irritant, however, as allergy requires a specific interaction with the immune system and is thus dependent on the (possibly unique) sensitivity of the organism involved while an irritant, classically, acts in a non-specific manner.
It is not proven that oysters can feel pain, but it is known that they react to irritation. When an irritating object becomes trapped within an oyster's shell, it deposits layers of calcium carbonate (CaCO3), slowly increasing in size and producing a pearl. This serves no purpose to the oyster, pearls do not attract mates for the oyster or perform any other function. It seems impossible to find an evolutionary advantage for the ability to produce the pearl, thus it can be explained only as a reaction to an irritation.
It has also been observed that an amoeba avoids being prodded with a pin, but there is not enough evidence to suggest how much it feels this. Irritation is apparently the only universal sense shared by even single-celled creatures.
Modern office work with use of office equipment has raised concerns about possible adverse health effects. Since the 1970s, reports have linked mucosal, skin, and general symptoms to work with self-copying paper. Emission of various volatile substances has been suggested as specific causes. These symptoms have been related to Sick Building Syndrome, which involves symptoms such as irritation to the eyes, skin, and upper airways, headache and fatigue.
How tobacco affects your body
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