Any substance that produces irritation in a tissue. Examples are: stinging nettles, which cause pain and swelling; certain insect bites or stings which do the same; and anti riot gases such as CS gas, which cause the eyes to water and provoke coughing. Regular, unprotected handling of certain substances – for example, oil – can irritate the skin and cause DERMATITIS. Some people are more sensitive than others to the eﬀect of irritants; sometimes an irritant will produce an allergic reaction (see ALLERGY) and in serious cases ANAPHYLAXIS, which may require medical treatment.
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