Abstract: A tamper evident closure (1) includes a housing (5) containing a blister pack (2) and a substrate (3), wherein the blister pack (2) contains a first reagent which is visible prior to first opening and the substrate (3) contains a second reagent. First opening of the closure ruptures the blister pack thereby exposing the first reagent to the second reagent and effecting a reaction that causes a visual change that signals the closure has been opened. The tamper evident closure of the present invention is primarily intended to be used as an anti-counterfeit measure on a spirit or pharmaceutical bottle. In the preferred embodiment, the closure incorporates a liquid that when brought into contact with a reagent chemical contained in an absorbent pad, effects an irreversible color change. This color change will indicate to a consumer the bottle has been previously opened or tampered with. The design makes it very difficult for a counterfeiter to cover up or eradicate the visible effects.