- "Oh, oh the silent treatment, huh? Well I got two words for you: Heat Syndrome. Look, look, I know I'm a parasite, but haven't I always been a helpful parasite? Now you may not care if you die from heat, but becoming a piece of beef jerky is not a lifelong ambition of mine!"
- ―Left Hand [[Vampire Hunter D: Bloodlust|[src]]]
An affliction common in dhampirs, usually happening once every six months, D's constitution and extraordinary physiology seems to give a prolonged resistance to this condition limiting it to only once every 5 years. During this time, long periods in sun light will weaken D greatly. The symptoms manifest with out warning, even the parasite can't detect or predict when it will happen. The symptoms are a sudden feeling of exhaustion and an ever increasing lassitude along with a fever so hot that there is no means to cool it under normal means. As long as the sufferer was exposed to sunlight their whole body would stiffen, leaving them paralyzed before eventually lost consciousness. Their body temperature would drop below that of a corpse, and their breaths would come several minutes apart leaving the sufferer unable to move or defend himself. Like Nobles however, this affliction will only affect him while he is on earth. On other planets, dimensions, or any other place other than this specific planet earth he will not be affected by sunlight.
Burial- In order to recover, they need to be buried, somewhere shady with only their heads exposed while they rest, although how long that would take varied greatly. In D's case, the average was about two days, although in one case it had taken him two weeks to recover. See Burial
In the movie Vampire Hunter D: Bloodlust it is refereed to as heat syndrome wrongfully. The weakness is exclusive to sunlight and not at all heat related like the human affliction of getting a heat stroke occurs in humans.
As shown in the Novel Scenes From An Unholy War, a hotel in the center of the Village of Geneve. A rather large Inn to accommodate merchants, it stands in the middle of two major highways in the center of town. Sheriff Rust presiding over the village as law-enforcement has trained the staff on how to treat Sunlight Syndrome. He has come into contact with D in the past, implying he has helped him in this situation before.