Air carrier Captain reported 'dirty socks' odor during climb which dissipated during cruise. The odor resumed during descent until landing where ultimately switched to ground air causing odor to dissipate.

Narrative

Cabin air quality event. At Gate on APU very mild dirty socks smell nothing worse than normal. On takeoff the smell became strong; 'Level 1' dirty sock/musty/waxy smell. No suspected or known causes. Odor dissipated climbing through FL180. Upon Leveling off at FL350 odor was gone. Flight Attendant (FA) reported mild dizziness and throat irritation but felt fine once at cruise altitude. No complaints from any passengers. Odor throughout the whole cabin and flight deck. On climb out we checked all systems and everything was fine. Started looking into QRH and sent dispatch message. Quickly the smell dissipated so we decided not to follow QRH. Repeatedly checked on FA's and everyone felt fine. FA's filled out air quality form. I decided to put on oxygen for 10 minutes and then take off my mask to see if I could smell any signs of lingering odor which I could not detect. Continued flight to ZZZ as planned. On descent passing through FL227 the same odor returned and became stronger as we continued approach and landing. On descent we again reviewed QRH to be prepared in case conditions worsened. Once on ground we switched to APU then ground air and odor once again dissipated. Debriefed with FA's; Flight Operations Duty Officer; dispatch; and maintenance. No crew or passengers required medical assistance.