The heat in a curry comes from the capsaicin compound in chilli peppers. This causes the pain receptors in your mouth to release a molecule called PIP2, which creates a burning sensation, even though there’s no actual tissue damage.
Your genes control how tightly PIP2 is bound to the pain receptors, which in turn determines how sensitive you are to the spice, but repeated exposure to chilli will reduce the effect quite quickly. A 1991 study at Yale University found that daily exposure over six days was enough to significantly reduce the perceived burn.
So it’s possible to build up a tolerance, but even true ‘chilli heads’ will always feel the heat from a vindaloo – they just relish the extreme sensation.
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