If the itchiness starts when the neck sweats, it is possible that prickly heat has already formed in the area, and after the formation of prickly heat, the sweat may stimulate the inflammatory tissue around the prickly heat and produce certain itching symptoms due to continued sweating. The formation of prickly heat is mainly due to the formation of a sweat duct dilatation due to poor sweating in the area, or rupture, resulting in a local inflammatory papule, which may appear as a crystalline milia, or red milia, or a deep milia. In addition, there may also be eczema in the area, when eczema occurs, due to sweating reactions, but also due to sweat irritation of the eczema area inflammatory tissue, will also produce itching symptoms. In this case, you need to try to avoid local sweating and actively treat the original prickly heat or eczema.