What Causes Severe Itching On The Head Of Penis Post Unprotected Sex?

Hi this guy I m dating we recently started having unprotected sex now the first two times we had unprotected sex he an I were fine 3rd time he says he starting to itch inside by his head part but he s not burning or having any discharge at all but now it s consistently itching he used joke strap cream to help relieve the itch but it just starts back after awhile we both got tested recently back in December an jan an everything came back negative so is there anything you can tell us about it