Ravinder Kaur, 34, was charged with administering a poisonous or noxious substance and stood trial for three weeks at Blackfriars Crown Court.

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She denies administering a poisonous or noxious substance with intent.

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Even the use of ammonium hydroxide can be a double-edged sword, since ammonia is perceived to be a noxious substance (although BPI effectively explains the benefits of the process on its website).

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Since substance P is activated in response to noxious stimuli, scientists long thought that it might be a central messenger for pain.

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