I think it might be an activated immune system OR being in a weakened state. As for why...
Haibara/Shiho: held in captivity and potentially injured when caught rebelling after news of her sister's death. Thus, leading to the immune system running higher than usual.
Mary: This chapter...
Okay, it's one thing when it comes to his thoughts on the first girl and not understanding that her love is quite literally over flowing(since she basically defaulted to that way), but the latest chapter just proves that he's a fool as it's shown in just enough stages that the love meter is...
This is interesting but I wish the "affection meter" was less spontaneous and more gradual and better defined. Also, the story felt a bit too quick and unexplained at certain points. One example being before and after he helped the Silver Haired girls sister. She apparently really disliked him...
I mean... he's not really that dense as he suddenly got that ability and yet it fluctuates far to easily. There's no proper baseline or total so if feels like the reading it give is superfluous. With that in mind (as well the fact that when he first saw Mariko's "emotion/love" meter, and it was...