Air Carrier Captain reported an intermittent fume event during initial climb and again during destination descent which eventually dissipated and did not return. At gate arrival the Captain submitted company reports and First Officer was treated for physiological symptoms.

Narrative

Aircraft X Immediately after takeoff I noticed a faint smell of dirty socks which only lasted a few seconds. The First Officer (FO) did not notice the smell. When we began our initial descent into our arrival airport; I believe we leveled off around 26;000 ft.; the First Officer asked me if I smelled something. Coincidentally; I noticed the smell at the exact same time he said something. He either smelled it first; or I did not realize I smelled something until he brought it to my attention. We were then given another descent and the odor dissipated before we had time to apply the appropriate procedures. In the descent; we had time to open our manuals to the fume removal procedure as we anticipated possibly another instance on level off. We leveled off around 11;000 ft.; but we did not encounter any more odors for the remainder of the flight. Upon arrival at the gate; the First Officer felt dizzy; lightheaded; and possibly had a few other symptoms. The cabin crew did not encounter any indication of an odor in the cabin. I filled out the paper air quality form maintenance personnel requested and I also filled out the digital online form; I notified Dispatch; and I also notified the Chief Pilot on duty per our safety reporting requirements. The online form would not allow me access to the description section. I tried to login to the form twice however; each time I was unable to fill out the description section. I submitted it with the information that it allowed me to input. The First Officer went on to seek an evaluation due to his symptoms.